The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Timothy S. Tracy - One of the best experts on this subject based on the ideXlab platform.

  • mechanism based inactivation of cytochrome p450 2c9 by tienilic acid and Suprofen a comparison of kinetics and probe substrate selection
    Drug Metabolism and Disposition, 2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and (±)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of ∼9 ml/min/μmol), the inactivation kinetics were characterized by a sigmoidal profile. (±)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (∼1 ml/min/μmol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (±)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/μmol) and ∼3-fold higher (3 ml/min/μmol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (±)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (Ks) of 2 μM and an in vitro half-life of 5 min compared with a Ks of 21 μM and a 50 min in vitro half-life for (±)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

  • Mechanism-based inactivation of cytochrome P450 2C9 by tienilic acid and (+/-)-Suprofen: a comparison of kinetics and probe substrate selection." Drug Metab Dispos
    2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and ()-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of 9 ml/min/ mol), the inactivation kinetics were characterized by a sigmoidal profile. ()-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (1 ml/min/mol). In con-trast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxyla-tion by tienilic acid and ()-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/mol) and3-fold higher (3 ml/min/mol), respectively, relative to that of the other probe substrates, which argues fo

  • mechanism based inactivation of cytochrome p450 2c9 by tienilic acid and Suprofen a comparison of kinetics and probe substrate selection
    Drug Metabolism and Disposition, 2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare k(inact), K(I) and inactivation efficiency (k(inact)/K(I)) of cytochrome P450 (P450) 2C9 by tienilic acid and (+/-)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of approximately 9 ml/min/micromol), the inactivation kinetics were characterized by a sigmoidal profile. (+/-)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (approximately 1 ml/min/micromol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (+/-)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/micromol) and approximately 3-fold higher (3 ml/min/micromol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (+/-)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (K(s)) of 2 microM and an in vitro half-life of 5 min compared with a K(s) of 21 microM and a 50 min in vitro half-life for (+/-)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

  • Mechanism-based inactivation of cytochrome P450 2C9 by tienilic acid and (+/-)-Suprofen: a comparison of kinetics and probe substrate selection.
    Drug Metabolism and Disposition, 2008
    Co-Authors: J. Matthew Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and (±)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of ∼9 ml/min/μmol), the inactivation kinetics were characterized by a sigmoidal profile. (±)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (∼1 ml/min/μmol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (±)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/μmol) and ∼3-fold higher (3 ml/min/μmol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (±)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (Ks) of 2 μM and an in vitro half-life of 5 min compared with a Ks of 21 μM and a 50 min in vitro half-life for (±)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

Larissa M Balogh - One of the best experts on this subject based on the ideXlab platform.

  • mechanism based inactivation of cytochrome p450 2c9 by tienilic acid and Suprofen a comparison of kinetics and probe substrate selection
    Drug Metabolism and Disposition, 2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and (±)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of ∼9 ml/min/μmol), the inactivation kinetics were characterized by a sigmoidal profile. (±)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (∼1 ml/min/μmol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (±)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/μmol) and ∼3-fold higher (3 ml/min/μmol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (±)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (Ks) of 2 μM and an in vitro half-life of 5 min compared with a Ks of 21 μM and a 50 min in vitro half-life for (±)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

  • Mechanism-based inactivation of cytochrome P450 2C9 by tienilic acid and (+/-)-Suprofen: a comparison of kinetics and probe substrate selection." Drug Metab Dispos
    2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and ()-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of 9 ml/min/ mol), the inactivation kinetics were characterized by a sigmoidal profile. ()-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (1 ml/min/mol). In con-trast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxyla-tion by tienilic acid and ()-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/mol) and3-fold higher (3 ml/min/mol), respectively, relative to that of the other probe substrates, which argues fo

  • mechanism based inactivation of cytochrome p450 2c9 by tienilic acid and Suprofen a comparison of kinetics and probe substrate selection
    Drug Metabolism and Disposition, 2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare k(inact), K(I) and inactivation efficiency (k(inact)/K(I)) of cytochrome P450 (P450) 2C9 by tienilic acid and (+/-)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of approximately 9 ml/min/micromol), the inactivation kinetics were characterized by a sigmoidal profile. (+/-)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (approximately 1 ml/min/micromol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (+/-)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/micromol) and approximately 3-fold higher (3 ml/min/micromol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (+/-)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (K(s)) of 2 microM and an in vitro half-life of 5 min compared with a K(s) of 21 microM and a 50 min in vitro half-life for (+/-)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

  • Mechanism-based inactivation of cytochrome P450 2C9 by tienilic acid and (+/-)-Suprofen: a comparison of kinetics and probe substrate selection.
    Drug Metabolism and Disposition, 2008
    Co-Authors: J. Matthew Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and (±)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of ∼9 ml/min/μmol), the inactivation kinetics were characterized by a sigmoidal profile. (±)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (∼1 ml/min/μmol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (±)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/μmol) and ∼3-fold higher (3 ml/min/μmol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (±)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (Ks) of 2 μM and an in vitro half-life of 5 min compared with a Ks of 21 μM and a 50 min in vitro half-life for (±)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

Michael Zientek - One of the best experts on this subject based on the ideXlab platform.

  • mechanism based inactivation of cytochrome p450 2c9 by tienilic acid and Suprofen a comparison of kinetics and probe substrate selection
    Drug Metabolism and Disposition, 2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and (±)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of ∼9 ml/min/μmol), the inactivation kinetics were characterized by a sigmoidal profile. (±)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (∼1 ml/min/μmol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (±)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/μmol) and ∼3-fold higher (3 ml/min/μmol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (±)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (Ks) of 2 μM and an in vitro half-life of 5 min compared with a Ks of 21 μM and a 50 min in vitro half-life for (±)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

  • Mechanism-based inactivation of cytochrome P450 2C9 by tienilic acid and (+/-)-Suprofen: a comparison of kinetics and probe substrate selection." Drug Metab Dispos
    2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and ()-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of 9 ml/min/ mol), the inactivation kinetics were characterized by a sigmoidal profile. ()-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (1 ml/min/mol). In con-trast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxyla-tion by tienilic acid and ()-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/mol) and3-fold higher (3 ml/min/mol), respectively, relative to that of the other probe substrates, which argues fo

  • mechanism based inactivation of cytochrome p450 2c9 by tienilic acid and Suprofen a comparison of kinetics and probe substrate selection
    Drug Metabolism and Disposition, 2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare k(inact), K(I) and inactivation efficiency (k(inact)/K(I)) of cytochrome P450 (P450) 2C9 by tienilic acid and (+/-)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of approximately 9 ml/min/micromol), the inactivation kinetics were characterized by a sigmoidal profile. (+/-)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (approximately 1 ml/min/micromol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (+/-)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/micromol) and approximately 3-fold higher (3 ml/min/micromol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (+/-)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (K(s)) of 2 microM and an in vitro half-life of 5 min compared with a K(s) of 21 microM and a 50 min in vitro half-life for (+/-)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

  • Mechanism-based inactivation of cytochrome P450 2C9 by tienilic acid and (+/-)-Suprofen: a comparison of kinetics and probe substrate selection.
    Drug Metabolism and Disposition, 2008
    Co-Authors: J. Matthew Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and (±)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of ∼9 ml/min/μmol), the inactivation kinetics were characterized by a sigmoidal profile. (±)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (∼1 ml/min/μmol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (±)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/μmol) and ∼3-fold higher (3 ml/min/μmol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (±)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (Ks) of 2 μM and an in vitro half-life of 5 min compared with a Ks of 21 μM and a 50 min in vitro half-life for (±)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

Vikas Kumar - One of the best experts on this subject based on the ideXlab platform.

  • mechanism based inactivation of cytochrome p450 2c9 by tienilic acid and Suprofen a comparison of kinetics and probe substrate selection
    Drug Metabolism and Disposition, 2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and (±)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of ∼9 ml/min/μmol), the inactivation kinetics were characterized by a sigmoidal profile. (±)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (∼1 ml/min/μmol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (±)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/μmol) and ∼3-fold higher (3 ml/min/μmol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (±)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (Ks) of 2 μM and an in vitro half-life of 5 min compared with a Ks of 21 μM and a 50 min in vitro half-life for (±)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

  • Mechanism-based inactivation of cytochrome P450 2C9 by tienilic acid and (+/-)-Suprofen: a comparison of kinetics and probe substrate selection." Drug Metab Dispos
    2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and ()-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of 9 ml/min/ mol), the inactivation kinetics were characterized by a sigmoidal profile. ()-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (1 ml/min/mol). In con-trast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxyla-tion by tienilic acid and ()-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/mol) and3-fold higher (3 ml/min/mol), respectively, relative to that of the other probe substrates, which argues fo

  • mechanism based inactivation of cytochrome p450 2c9 by tienilic acid and Suprofen a comparison of kinetics and probe substrate selection
    Drug Metabolism and Disposition, 2009
    Co-Authors: Matthew J Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare k(inact), K(I) and inactivation efficiency (k(inact)/K(I)) of cytochrome P450 (P450) 2C9 by tienilic acid and (+/-)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of approximately 9 ml/min/micromol), the inactivation kinetics were characterized by a sigmoidal profile. (+/-)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (approximately 1 ml/min/micromol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (+/-)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/micromol) and approximately 3-fold higher (3 ml/min/micromol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (+/-)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (K(s)) of 2 microM and an in vitro half-life of 5 min compared with a K(s) of 21 microM and a 50 min in vitro half-life for (+/-)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

  • Mechanism-based inactivation of cytochrome P450 2C9 by tienilic acid and (+/-)-Suprofen: a comparison of kinetics and probe substrate selection.
    Drug Metabolism and Disposition, 2008
    Co-Authors: J. Matthew Hutzler, Larissa M Balogh, Michael Zientek, Vikas Kumar, Timothy S. Tracy
    Abstract:

    In vitro experiments were conducted to compare kinact, KI and inactivation efficiency (kinact/KI) of cytochrome P450 (P450) 2C9 by tienilic acid and (±)-Suprofen using (S)-flurbiprofen, diclofenac, and (S)-warfarin as reporter substrates. Although the inactivation of P450 2C9 by tienilic acid when (S)-flurbiprofen and diclofenac were used as substrates was similar (efficiency of ∼9 ml/min/μmol), the inactivation kinetics were characterized by a sigmoidal profile. (±)-Suprofen inactivation of (S)-flurbiprofen and diclofenac hydroxylation was also described by a sigmoidal profile, although inactivation was markedly less efficient (∼1 ml/min/μmol). In contrast, inactivation of P450 2C9-mediated (S)-warfarin 7-hydroxylation by tienilic acid and (±)-Suprofen was best fit to a hyperbolic equation, where inactivation efficiency was moderately higher (10 ml/min/μmol) and ∼3-fold higher (3 ml/min/μmol), respectively, relative to that of the other probe substrates, which argues for careful consideration of reporter substrate when mechanism-based inactivation of P450 2C9 is assessed in vitro. Further investigations into the increased inactivation seen with tienilic acid relative to that with (±)-Suprofen revealed that tienilic acid is a higher affinity substrate with a spectral binding affinity constant (Ks) of 2 μM and an in vitro half-life of 5 min compared with a Ks of 21 μM and a 50 min in vitro half-life for (±)-Suprofen. Lastly, a close analog of tienilic acid with the carboxylate functionality replaced by an oxirane ring was devoid of inactivation properties, which suggests that an ionic binding interaction with a positively charged residue in the P450 2C9 active site is critical for recognition and mechanism-based inactivation by these close structural analogs.

Jian Hua Liu - One of the best experts on this subject based on the ideXlab platform.

  • covalent binding of Suprofen to renal tissue of rat correlates with excretion of its acyl glucuronide
    Xenobiotica, 1995
    Co-Authors: Philip C Smith, Jian Hua Liu
    Abstract:

    1. Dosing rat with Suprofen produces Suprofen equivalents that are covalently bound to plasma and tissue proteins in vivo.2. Suprofen acyl glucuronide is reactive in vitro, resulting in Suprofen equivalents covalently bound to proteins of plasma and tissues in a time-dependent manner.3. Bile duct ligation of rat increases exposure to Suprofen acyl glucuronide in vivo, which leads to enhanced covalent binding of Suprofen equivalents to plasma proteins and to kidney tissue.4. Covalent binding of Suprofen equivalents to kidney tissue correlates with excretion of Suprofen and Suprofen glucuronide by the kidney.

  • covalent binding of Suprofen acyl glucuronide to albumin in vitro
    Xenobiotica, 1993
    Co-Authors: Philip C Smith, Jian Hua Liu
    Abstract:

    1. Suprofen acyl glucuronide, a major metabolite of Suprofen in man, is labile, undergoing acyl migration to isomeric conjugates which are not cleaved by beta-glucuronidase. 2. The pH-dependent degradation of diastereomeric Suprofen glucuronides in aqueous buffer increases rapidly near physiological pH with an apparent first-order half life of 1.4 h at pH 7.4. 3. Suprofen glucuronide and its isomeric conjugates are reactive with albumin in a pH-dependent manner which corresponds to the stability of the acyl glucuronide. Several per cent of the conjugates added to albumin in solution become covalently bound. 4. The covalent binding of Suprofen equivalents to albumin is greatly enhanced by the addition of either cyanide or cyanoborohydride anion, which supports the presence of an imine in the process of binding. Release of isomeric conjugates by treatment of the albumin adduct with dilute acid also supports covalent binding via an imine. 5. The covalent binding of Suprofen to proteins through its reactive acyl glucuronide may be of toxicological importance and relevant to the acute renal toxicity observed for Suprofen in man.