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Ivonne M C M Rietjens - One of the best experts on this subject based on the ideXlab platform.
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kinetics of Cytochromes p 450 ia1 and iib1 in reconstituted systems with dilauroyl and distearoyl glycerophosphocholine
FEBS Journal, 1993Co-Authors: Walter G Balvers, Cees Veeger, Marelle G Boersma, Ivonne M C M RietjensAbstract:In the present study the effect of changing the fatty acyl moiety of phosphatidylcholine from dilauroyl to distearoyl on the kinetic parameters of O-dealkylation of alkoxyresorufins and ethoxycoumarin dependent on reconstituted Cytochromes P-450 IA1 and IIB1 has been investigated. The results demonstrate that (a) the maximum rate of O-dealkylation (V) for both P-450 enzymes was about two times higher in the L-alpha-dilauroyl-sn-glycero-3-phosphocholine (Lau2GroPCho) system and (b) changes in the fatty acyl moiety of phosphatidylcholine (acyl2GroPCho) from dilauroyl to distearoyl affected the apparent Km for the substrate (Kms) of P-450 IA1 and IIB1 in a different way. In addition, (c) the kinetic parameters appeared to be dependent on the acyl2GroPCho/P-450 ratio and a change in this ratio affected the kinetic parameters of P-450 IA1 and IIB1 in a different manner. From these last two observations it was concluded that the mechanism by which phospholipids influence P-450-IIB1-dependent O-dealkylation of ethoxycoumarin is different from that by which they influence P-450-IIB1-dependent O-dealkylation of this substrate. Furthermore, the results of the present study demonstrate that the increase in the rate of O-dealkylation of ethoxycoumarin, reported in the literature for reconstituted systems in the presence of Lau2GroPCho, results from an effect of Lau2GroPCho on both the Kms and the V. In a number of additional experiments possible mechanisms underlying the observed differential effect of Lau2GroPCho and Ste2GroPCho on the Kms and V of P-450 IA1 and IIB1 were investigated. This was done by studying the effect of the two acyl2GroPCho species on the kinetic parameters of some of the different steps of the P-450 cycle, namely substrate binding, oxygen binding and the rate of electron transfer. The results demonstrate an influence of Lau2GroPCho and Ste2GroPCho on (a) substrate binding to Cytochrome P-450, (b) the affinity of Cytochromes P-450 for NADPH-Cytochrome Reductase and thus on (c) the electron flow through the reconstituted system. Based on the results from these experiments it was concluded that the increased V of P-450 IA1 and IIB1 in the presence of Lau2GroPCho compared to the systems with Ste2GroPCho was at least in part due to an increased affinity of both P-450 enzymes for NADPH-Cytochrome Reductase in the presence of Lau2GroPCho compared to Ste2GroPCho.(ABSTRACT TRUNCATED AT 400 WORDS)
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experimental and theoretical study on the redox cycling of resorufin by solubilized and membrane bound nadph Cytochrome Reductase
Chemical Research in Toxicology, 1992Co-Authors: Walter G Balvers, Marelle G Boersma, Jacques Vervoort, Ivonne M C M RietjensAbstract:The present study describes both experimental and theoretical data on the redox cycling of resorufins catalyzed by NADPH-Cytochrome Reductase. At 1-5 microM concentrations at physiological pH, the redox cycling of ethoxy- and pentoxyresorufin was shown to be far more efficient than the redox cycling of their product from the Cytochrome P-450 dependent O-dealkylation, resorufin (7-hydroxyphenoxazone). This was shown to result from the fact that (i) the protonated form of the resorufin is a much better substrate for redox cycling than the deprotonated resorufin O-anion and (ii) at physiological pH the redox cycling active protonated form is present at only 1-4% of the total amount of resorufin. In addition to experimental data, AM1 molecular orbital computer calculations provided evidence for the difference in redox cycling capacity between the resorufin O-anion and its protonated form. The energy of the lowest unoccupied molecular orbital (ELUMO) of the resorufin O-anion is higher than the ELUMO value for the protonated form. This low ELUMO value of the protonated form can be taken as a parameter for its easier reduction. Furthermore, computer calculations demonstrated one-electron reduction of the protonated form to be energetically favorable by 363.5 kJ/mol, compared to one-electron reduction of the deprotonated O-anionic form. Additional AM1 molecular orbital computer calculations indicated that the one-electron-reduced resorufin will become protonated at the O-atom of the intramolecular semiquinone imine moiety before reduction by a second electron becomes likely. Finally, redox cycling of resorufin by solubilized and membrane-incorporated NADPH-Cytochrome Reductase provided evidence that membrane surroundings increase the concentration of the protonated form of resorufin.(ABSTRACT TRUNCATED AT 250 WORDS)
Walter G Balvers - One of the best experts on this subject based on the ideXlab platform.
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kinetics of Cytochromes p 450 ia1 and iib1 in reconstituted systems with dilauroyl and distearoyl glycerophosphocholine
FEBS Journal, 1993Co-Authors: Walter G Balvers, Cees Veeger, Marelle G Boersma, Ivonne M C M RietjensAbstract:In the present study the effect of changing the fatty acyl moiety of phosphatidylcholine from dilauroyl to distearoyl on the kinetic parameters of O-dealkylation of alkoxyresorufins and ethoxycoumarin dependent on reconstituted Cytochromes P-450 IA1 and IIB1 has been investigated. The results demonstrate that (a) the maximum rate of O-dealkylation (V) for both P-450 enzymes was about two times higher in the L-alpha-dilauroyl-sn-glycero-3-phosphocholine (Lau2GroPCho) system and (b) changes in the fatty acyl moiety of phosphatidylcholine (acyl2GroPCho) from dilauroyl to distearoyl affected the apparent Km for the substrate (Kms) of P-450 IA1 and IIB1 in a different way. In addition, (c) the kinetic parameters appeared to be dependent on the acyl2GroPCho/P-450 ratio and a change in this ratio affected the kinetic parameters of P-450 IA1 and IIB1 in a different manner. From these last two observations it was concluded that the mechanism by which phospholipids influence P-450-IIB1-dependent O-dealkylation of ethoxycoumarin is different from that by which they influence P-450-IIB1-dependent O-dealkylation of this substrate. Furthermore, the results of the present study demonstrate that the increase in the rate of O-dealkylation of ethoxycoumarin, reported in the literature for reconstituted systems in the presence of Lau2GroPCho, results from an effect of Lau2GroPCho on both the Kms and the V. In a number of additional experiments possible mechanisms underlying the observed differential effect of Lau2GroPCho and Ste2GroPCho on the Kms and V of P-450 IA1 and IIB1 were investigated. This was done by studying the effect of the two acyl2GroPCho species on the kinetic parameters of some of the different steps of the P-450 cycle, namely substrate binding, oxygen binding and the rate of electron transfer. The results demonstrate an influence of Lau2GroPCho and Ste2GroPCho on (a) substrate binding to Cytochrome P-450, (b) the affinity of Cytochromes P-450 for NADPH-Cytochrome Reductase and thus on (c) the electron flow through the reconstituted system. Based on the results from these experiments it was concluded that the increased V of P-450 IA1 and IIB1 in the presence of Lau2GroPCho compared to the systems with Ste2GroPCho was at least in part due to an increased affinity of both P-450 enzymes for NADPH-Cytochrome Reductase in the presence of Lau2GroPCho compared to Ste2GroPCho.(ABSTRACT TRUNCATED AT 400 WORDS)
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experimental and theoretical study on the redox cycling of resorufin by solubilized and membrane bound nadph Cytochrome Reductase
Chemical Research in Toxicology, 1992Co-Authors: Walter G Balvers, Marelle G Boersma, Jacques Vervoort, Ivonne M C M RietjensAbstract:The present study describes both experimental and theoretical data on the redox cycling of resorufins catalyzed by NADPH-Cytochrome Reductase. At 1-5 microM concentrations at physiological pH, the redox cycling of ethoxy- and pentoxyresorufin was shown to be far more efficient than the redox cycling of their product from the Cytochrome P-450 dependent O-dealkylation, resorufin (7-hydroxyphenoxazone). This was shown to result from the fact that (i) the protonated form of the resorufin is a much better substrate for redox cycling than the deprotonated resorufin O-anion and (ii) at physiological pH the redox cycling active protonated form is present at only 1-4% of the total amount of resorufin. In addition to experimental data, AM1 molecular orbital computer calculations provided evidence for the difference in redox cycling capacity between the resorufin O-anion and its protonated form. The energy of the lowest unoccupied molecular orbital (ELUMO) of the resorufin O-anion is higher than the ELUMO value for the protonated form. This low ELUMO value of the protonated form can be taken as a parameter for its easier reduction. Furthermore, computer calculations demonstrated one-electron reduction of the protonated form to be energetically favorable by 363.5 kJ/mol, compared to one-electron reduction of the deprotonated O-anionic form. Additional AM1 molecular orbital computer calculations indicated that the one-electron-reduced resorufin will become protonated at the O-atom of the intramolecular semiquinone imine moiety before reduction by a second electron becomes likely. Finally, redox cycling of resorufin by solubilized and membrane-incorporated NADPH-Cytochrome Reductase provided evidence that membrane surroundings increase the concentration of the protonated form of resorufin.(ABSTRACT TRUNCATED AT 250 WORDS)
Marelle G Boersma - One of the best experts on this subject based on the ideXlab platform.
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kinetics of Cytochromes p 450 ia1 and iib1 in reconstituted systems with dilauroyl and distearoyl glycerophosphocholine
FEBS Journal, 1993Co-Authors: Walter G Balvers, Cees Veeger, Marelle G Boersma, Ivonne M C M RietjensAbstract:In the present study the effect of changing the fatty acyl moiety of phosphatidylcholine from dilauroyl to distearoyl on the kinetic parameters of O-dealkylation of alkoxyresorufins and ethoxycoumarin dependent on reconstituted Cytochromes P-450 IA1 and IIB1 has been investigated. The results demonstrate that (a) the maximum rate of O-dealkylation (V) for both P-450 enzymes was about two times higher in the L-alpha-dilauroyl-sn-glycero-3-phosphocholine (Lau2GroPCho) system and (b) changes in the fatty acyl moiety of phosphatidylcholine (acyl2GroPCho) from dilauroyl to distearoyl affected the apparent Km for the substrate (Kms) of P-450 IA1 and IIB1 in a different way. In addition, (c) the kinetic parameters appeared to be dependent on the acyl2GroPCho/P-450 ratio and a change in this ratio affected the kinetic parameters of P-450 IA1 and IIB1 in a different manner. From these last two observations it was concluded that the mechanism by which phospholipids influence P-450-IIB1-dependent O-dealkylation of ethoxycoumarin is different from that by which they influence P-450-IIB1-dependent O-dealkylation of this substrate. Furthermore, the results of the present study demonstrate that the increase in the rate of O-dealkylation of ethoxycoumarin, reported in the literature for reconstituted systems in the presence of Lau2GroPCho, results from an effect of Lau2GroPCho on both the Kms and the V. In a number of additional experiments possible mechanisms underlying the observed differential effect of Lau2GroPCho and Ste2GroPCho on the Kms and V of P-450 IA1 and IIB1 were investigated. This was done by studying the effect of the two acyl2GroPCho species on the kinetic parameters of some of the different steps of the P-450 cycle, namely substrate binding, oxygen binding and the rate of electron transfer. The results demonstrate an influence of Lau2GroPCho and Ste2GroPCho on (a) substrate binding to Cytochrome P-450, (b) the affinity of Cytochromes P-450 for NADPH-Cytochrome Reductase and thus on (c) the electron flow through the reconstituted system. Based on the results from these experiments it was concluded that the increased V of P-450 IA1 and IIB1 in the presence of Lau2GroPCho compared to the systems with Ste2GroPCho was at least in part due to an increased affinity of both P-450 enzymes for NADPH-Cytochrome Reductase in the presence of Lau2GroPCho compared to Ste2GroPCho.(ABSTRACT TRUNCATED AT 400 WORDS)
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experimental and theoretical study on the redox cycling of resorufin by solubilized and membrane bound nadph Cytochrome Reductase
Chemical Research in Toxicology, 1992Co-Authors: Walter G Balvers, Marelle G Boersma, Jacques Vervoort, Ivonne M C M RietjensAbstract:The present study describes both experimental and theoretical data on the redox cycling of resorufins catalyzed by NADPH-Cytochrome Reductase. At 1-5 microM concentrations at physiological pH, the redox cycling of ethoxy- and pentoxyresorufin was shown to be far more efficient than the redox cycling of their product from the Cytochrome P-450 dependent O-dealkylation, resorufin (7-hydroxyphenoxazone). This was shown to result from the fact that (i) the protonated form of the resorufin is a much better substrate for redox cycling than the deprotonated resorufin O-anion and (ii) at physiological pH the redox cycling active protonated form is present at only 1-4% of the total amount of resorufin. In addition to experimental data, AM1 molecular orbital computer calculations provided evidence for the difference in redox cycling capacity between the resorufin O-anion and its protonated form. The energy of the lowest unoccupied molecular orbital (ELUMO) of the resorufin O-anion is higher than the ELUMO value for the protonated form. This low ELUMO value of the protonated form can be taken as a parameter for its easier reduction. Furthermore, computer calculations demonstrated one-electron reduction of the protonated form to be energetically favorable by 363.5 kJ/mol, compared to one-electron reduction of the deprotonated O-anionic form. Additional AM1 molecular orbital computer calculations indicated that the one-electron-reduced resorufin will become protonated at the O-atom of the intramolecular semiquinone imine moiety before reduction by a second electron becomes likely. Finally, redox cycling of resorufin by solubilized and membrane-incorporated NADPH-Cytochrome Reductase provided evidence that membrane surroundings increase the concentration of the protonated form of resorufin.(ABSTRACT TRUNCATED AT 250 WORDS)
Cees Veeger - One of the best experts on this subject based on the ideXlab platform.
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kinetics of Cytochromes p 450 ia1 and iib1 in reconstituted systems with dilauroyl and distearoyl glycerophosphocholine
FEBS Journal, 1993Co-Authors: Walter G Balvers, Cees Veeger, Marelle G Boersma, Ivonne M C M RietjensAbstract:In the present study the effect of changing the fatty acyl moiety of phosphatidylcholine from dilauroyl to distearoyl on the kinetic parameters of O-dealkylation of alkoxyresorufins and ethoxycoumarin dependent on reconstituted Cytochromes P-450 IA1 and IIB1 has been investigated. The results demonstrate that (a) the maximum rate of O-dealkylation (V) for both P-450 enzymes was about two times higher in the L-alpha-dilauroyl-sn-glycero-3-phosphocholine (Lau2GroPCho) system and (b) changes in the fatty acyl moiety of phosphatidylcholine (acyl2GroPCho) from dilauroyl to distearoyl affected the apparent Km for the substrate (Kms) of P-450 IA1 and IIB1 in a different way. In addition, (c) the kinetic parameters appeared to be dependent on the acyl2GroPCho/P-450 ratio and a change in this ratio affected the kinetic parameters of P-450 IA1 and IIB1 in a different manner. From these last two observations it was concluded that the mechanism by which phospholipids influence P-450-IIB1-dependent O-dealkylation of ethoxycoumarin is different from that by which they influence P-450-IIB1-dependent O-dealkylation of this substrate. Furthermore, the results of the present study demonstrate that the increase in the rate of O-dealkylation of ethoxycoumarin, reported in the literature for reconstituted systems in the presence of Lau2GroPCho, results from an effect of Lau2GroPCho on both the Kms and the V. In a number of additional experiments possible mechanisms underlying the observed differential effect of Lau2GroPCho and Ste2GroPCho on the Kms and V of P-450 IA1 and IIB1 were investigated. This was done by studying the effect of the two acyl2GroPCho species on the kinetic parameters of some of the different steps of the P-450 cycle, namely substrate binding, oxygen binding and the rate of electron transfer. The results demonstrate an influence of Lau2GroPCho and Ste2GroPCho on (a) substrate binding to Cytochrome P-450, (b) the affinity of Cytochromes P-450 for NADPH-Cytochrome Reductase and thus on (c) the electron flow through the reconstituted system. Based on the results from these experiments it was concluded that the increased V of P-450 IA1 and IIB1 in the presence of Lau2GroPCho compared to the systems with Ste2GroPCho was at least in part due to an increased affinity of both P-450 enzymes for NADPH-Cytochrome Reductase in the presence of Lau2GroPCho compared to Ste2GroPCho.(ABSTRACT TRUNCATED AT 400 WORDS)
Shunsuke Noguchi - One of the best experts on this subject based on the ideXlab platform.
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bacillus stearothermophilus qcr operon encoding rieske fes protein Cytochrome b6 and a novel type Cytochrome c1 of quinol Cytochrome c Reductase
Journal of Biological Chemistry, 1996Co-Authors: Nobuhito Sone, Naofumi Tsuchiya, Masatomo Inoue, Shunsuke NoguchiAbstract:Abstract The qcr of Bacillus stearothermophilus K1041 encoding three subunits of the quinol-Cytochrome c oxidoReductase (Cytochrome Reductase, bc1 complex) was cloned and sequenced. The gene (qcrA) for a Rieske FeS protein of 19,144 Da with 169 amino acid residues, and the gene (qcrC) for Cytochrome c1 of 27,342 Da with 250 amino acid residues were found at adjacent upstream and downstream sides of the previously reported qcrB (petB) for Cytochrome b of subunit 25,425 Da with 224 residues (Sone, N., Sawa, G., Sone, T., and Noguchi, S.(1995) J. Biol. Chem. 270, 10612-10617). The three structural genes for thermophilic Bacillus Cytochrome Reductase form a transcriptional unit. In the deduced amino acid sequence for the FeS protein, the domain including four cysteines and two histidines binding the 2Fe-2S cluster was conserved. Its N-terminal part more closely resembled the cyanobacteria-plastid type than the proteobacteria-mitochondria type when their sequences were compared. The amino acid sequence of Cytochrome c1 was not similar to either type; the thermophilic Bacillus Cytochrome c1 is composed of an N-terminal part corresponding to subunit IV with three membrane-spanning segments, and a C-terminal part of Cytochrome c reminiscent of Cytochrome c-551 of thermophilic Bacillus. The subunit IV in the enzyme of cyanobacteria and plastids is the counterpart of C-terminal part of Cytochrome b of proteobacteria and mitochondria. These characteristics indicate that Bacillus Cytochrome bc1 complex is unique.
