The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
Sarvagya S. Katiyar - One of the best experts on this subject based on the ideXlab platform.
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Studies on the Inactivation of Leuconostoc Mesenteroides Nrrl B-512f Dextransucrase by o-Phthalaldehyde: Evidence for the Presence of an Essential Lysine Residue at the Active Site
Journal of Enzyme Inhibition, 1998Co-Authors: Arun Goyal, Sarvagya S. KatiyarAbstract:AbstractThe kinetics of inactivation of Leuconostoc mesenteroides NRRL B-512F dextransucrase by o-pthalaldehyde showed that the reaction followed pseudo-first order reaction. The loss of enzyme activity was concomitant with an increase in fluorescence at 417nm indicating that the inhibition involved the reaction of an ϵ-amino and a thiol group of the enzyme leading to the formation of an Isoindole Derivative. The stoichiometry of inaclivation showed that one Isoindole Derivative was formed per enzyme molecule. The substrates sucrose and glucose provided protection against o-phthalaldehyde inactivation which was also corroborated by fluorescence studies. Dextransucrase was not inactivated by 5,5'-dithiobis(2-nitrobenzoic acid), showing that the cysteine present in close proximity to the lysine is not essential for enzyme activity. Denaturation of dextransucrase by urea or heat treatment prior to o-phthalaldehyde addition resulted in a decrease of fluorescence intensity indicating that the native conformati...
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Identification of cysteine and lysine residues present at the active site of beef liver glutamate dehydrogenase by o-phthalaldehyde
Biochimica et Biophysica Acta, 1996Co-Authors: Anjali Pandey, Saifuddin Sheikh, Sarvagya S. KatiyarAbstract:Abstract Beef liver glutamate dehydrogenase (GDH) is inactivated by the bifunctional reagent, o -phthalaldehyde. The initial rate of inactivation follows pseudo first-order kinetics. The reaction of the enzyme with o-phthalaldehyde results in Isoindole Derivative formation which is characterized by typical fluorescence emission and excitation maximum at 410 nm and 337 nm, respectively. The inactivation of GDH by o -phthalaldehyde is partially prevented by α-ketoglutaric acid, whereas NADH does not provide any protection. This clearly indicates that cysteine and lysine residues are located near the α-ketoglutaric acid binding center. The dissociation constant of 2.2 mM was obtained for enzyme-α-ketoglutaric acid complex. Stoichiometry of o -phthalaldehyde binding with glutamate dehydrogenase showed that the formation of approximately one Isoindole Derivative per subunit of glutamate dehydrogenase is accompanied by complete loss of activity.
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Inactivation of Yeast Glutathione Reductase by O-Phthalaldehyde
Journal of Enzyme Inhibition, 1996Co-Authors: Anjali Pandey, Sarvagya S. KatiyarAbstract:AbstractYeast glutathione reductase was inactivated by the bifunctional reagent, o-phtbalaldehyde. The initial rate of inactivation followed pseudo-first order kinetics. Fluorescence spectral properties of modified enzyme indicated the formation of an Isoindole Derivative from cysteine and lysine residues present in close proximity as shown by typical fluorescence emmision and excitation maximum at 410 nm and 337 nm, respectively. The fluorescence spectral studies with o-phthalaldehyde in the presence and absence of N-ethylmaleimide indicated that both the inhibitors react with the same cysteine residue, which is non-essential for enzyme activity. The coenzyme NADPH did not protect the enzyme against the o-phthalaldehyde reaction while oxidised glutathione prevented o-phthalaldehyde inactivation. This could be due to reaction of the amino group of glutathione with o-phthalaldehyde. Stoichiometry of the reaction showed that the formation of approximately 2 Isoindole Derivatives per subunit of glutathione r...
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Involvement of a lysine residue in the inactivation of Leuconostoc mesenteroides NRRL B-512F dextransucrase by o-phthalaldehyde.
Iubmb Life, 1995Co-Authors: Arun Goyal, Sarvagya S. KatiyarAbstract:Leuconostoc mesenteroides NRRL B-512F dextransucrase was rapidly and irreversibly inactivated by o-phthalaldehyde. The dextransucrase-o-phthalaldehyde adduct showed a characteristic fluorescence maxima at 417 nm when excited at 337 nm. These results were consistent with the Isoindole Derivative formation in which the sulfhydryl group of cysteine and epsilon-amino group of lysine participate in the reaction. The stoichiometric determinations gave one Isoindole Derivative per enzyme molecule upon complete inactivation by o-phthalaldehyde. The enzyme showed no inhibition on treatment with thiol specific reagents. This indicated that cysteine is present in close proximity of the lysine and is involved in the Isoindole Derivative formation but is not participating in the catalysis. These results established for the first time that one lysine residue present at the active site is required for the activity of dextransucrase.
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Investigation of the nature of o-phthalaldehyde reaction with octopine dehydrogenase.
Journal of Enzyme Inhibition, 1994Co-Authors: Saifuddin Sheikh, Sarvagya S. KatiyarAbstract:AbstractThe effect of o-phthalaldehyde on octopine dehydrogenase inactivation has been studied. o-Phthalaldehyde hinds to the proximal cysteine and lysine residues of the enzyme leading to the formation of Isoindole Derivative. Double inhibition studies with o-phthalaldehyde and p-chloromercuricphenyl sulfonic acid have indicated that o-phthalaldehyde does not hind to the functional cysteine present at the active site. Protection experiments have shown that L-arginine prevented o-phthalaldehyde inactivation. This could he only due to the reaction of the amino group of L-arginine with o-phthalaldehyde as per the mechanism proposed elsewhere since L-arginine cannot bind to the enzyme prior to NADH. Other substrates such as pyruvate or NADH could not prevent the o-phthalaldehyde reaction with the enzyme. Fluorescence spectral studies demonstrated that in the presence of externally added amino acid no Isoindole Derivative formation occurs. However. a characteristic Isoindole Derivative is formed in the presen...
Ichiro Takahashi - One of the best experts on this subject based on the ideXlab platform.
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a stable monosubstituted Isoindole Derivative the crystal structure of 1 1 2 3 1h benzotriazol 1 yl 2 4 methylphenyl 2h Isoindole
Chemical & Pharmaceutical Bulletin, 1994Co-Authors: Ichiro Takahashi, Mikio Tsuzuki, Takashi Keumi, Hidehiko Kitajima, Shinzo Hosoi, Yoshisuke TsudaAbstract:1-(1, 2, 3-1H-benzotriazol-1-yl)-2-(4-methylphenyl)-2H-Isoindole (1a) is a stable Isoindole Derivative in the crystalline state. On the basis of the results of X-ray crystallographic analysis, this exceptional stability was explained as follows : the presence of a typical anti-parallel face-to-face stacking between Isoindole rings deprives the two reactive centers of an intermolecular approach.
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Studies on the double Mannich condensation reaction of o-phthalaldehyde with p-substituted anilines in the presence of 1,2,3-1H-benzotriazole
Heterocycles, 1994Co-Authors: Ichiro Takahashi, Mikio Tsuzuki, Hiroshi Yokota, Hidehiko KitajimaAbstract:The double Mannich condensation reaction in acetonitrile at room tempe- rature has been investigated. In the condensation reaction of o-phthal- aldehyde (1) with p-toluidine (2a; 1 equiv.) in the presence of 1,2,3- 1H-benzotriazole (Bt-H), the use of 3 equiv. of Bt-H afforded Bt-subs- tituted isoindoline Derivative (4a) exclusively for 8 h, and the use of 4 equiv. of Bt-H did for 4 h; further increment of reaction time induced the dissociation of Bt-H from (4a) to give 2H-Isoindole Derivative (5a). On the other hand, when methyl p-aminobenzoate (2b) was used ins- tead of (2a), the rate of the formation of isoindoline (4b) increased as the amount used of Bt-H was large (2 → 3 → 4 equiv.). Different from the 2-p-tolyl) counterpart, the increment of the reaction time did not induce the dissociation of Bt-H to afford 2H-Isoindole Derivative (5b)
Hidehiko Kitajima - One of the best experts on this subject based on the ideXlab platform.
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a stable monosubstituted Isoindole Derivative the crystal structure of 1 1 2 3 1h benzotriazol 1 yl 2 4 methylphenyl 2h Isoindole
Chemical & Pharmaceutical Bulletin, 1994Co-Authors: Ichiro Takahashi, Mikio Tsuzuki, Takashi Keumi, Hidehiko Kitajima, Shinzo Hosoi, Yoshisuke TsudaAbstract:1-(1, 2, 3-1H-benzotriazol-1-yl)-2-(4-methylphenyl)-2H-Isoindole (1a) is a stable Isoindole Derivative in the crystalline state. On the basis of the results of X-ray crystallographic analysis, this exceptional stability was explained as follows : the presence of a typical anti-parallel face-to-face stacking between Isoindole rings deprives the two reactive centers of an intermolecular approach.
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Studies on the double Mannich condensation reaction of o-phthalaldehyde with p-substituted anilines in the presence of 1,2,3-1H-benzotriazole
Heterocycles, 1994Co-Authors: Ichiro Takahashi, Mikio Tsuzuki, Hiroshi Yokota, Hidehiko KitajimaAbstract:The double Mannich condensation reaction in acetonitrile at room tempe- rature has been investigated. In the condensation reaction of o-phthal- aldehyde (1) with p-toluidine (2a; 1 equiv.) in the presence of 1,2,3- 1H-benzotriazole (Bt-H), the use of 3 equiv. of Bt-H afforded Bt-subs- tituted isoindoline Derivative (4a) exclusively for 8 h, and the use of 4 equiv. of Bt-H did for 4 h; further increment of reaction time induced the dissociation of Bt-H from (4a) to give 2H-Isoindole Derivative (5a). On the other hand, when methyl p-aminobenzoate (2b) was used ins- tead of (2a), the rate of the formation of isoindoline (4b) increased as the amount used of Bt-H was large (2 → 3 → 4 equiv.). Different from the 2-p-tolyl) counterpart, the increment of the reaction time did not induce the dissociation of Bt-H to afford 2H-Isoindole Derivative (5b)
Arun Goyal - One of the best experts on this subject based on the ideXlab platform.
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Studies on the Inactivation of Leuconostoc Mesenteroides Nrrl B-512f Dextransucrase by o-Phthalaldehyde: Evidence for the Presence of an Essential Lysine Residue at the Active Site
Journal of Enzyme Inhibition, 1998Co-Authors: Arun Goyal, Sarvagya S. KatiyarAbstract:AbstractThe kinetics of inactivation of Leuconostoc mesenteroides NRRL B-512F dextransucrase by o-pthalaldehyde showed that the reaction followed pseudo-first order reaction. The loss of enzyme activity was concomitant with an increase in fluorescence at 417nm indicating that the inhibition involved the reaction of an ϵ-amino and a thiol group of the enzyme leading to the formation of an Isoindole Derivative. The stoichiometry of inaclivation showed that one Isoindole Derivative was formed per enzyme molecule. The substrates sucrose and glucose provided protection against o-phthalaldehyde inactivation which was also corroborated by fluorescence studies. Dextransucrase was not inactivated by 5,5'-dithiobis(2-nitrobenzoic acid), showing that the cysteine present in close proximity to the lysine is not essential for enzyme activity. Denaturation of dextransucrase by urea or heat treatment prior to o-phthalaldehyde addition resulted in a decrease of fluorescence intensity indicating that the native conformati...
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Involvement of a lysine residue in the inactivation of Leuconostoc mesenteroides NRRL B-512F dextransucrase by o-phthalaldehyde.
Iubmb Life, 1995Co-Authors: Arun Goyal, Sarvagya S. KatiyarAbstract:Leuconostoc mesenteroides NRRL B-512F dextransucrase was rapidly and irreversibly inactivated by o-phthalaldehyde. The dextransucrase-o-phthalaldehyde adduct showed a characteristic fluorescence maxima at 417 nm when excited at 337 nm. These results were consistent with the Isoindole Derivative formation in which the sulfhydryl group of cysteine and epsilon-amino group of lysine participate in the reaction. The stoichiometric determinations gave one Isoindole Derivative per enzyme molecule upon complete inactivation by o-phthalaldehyde. The enzyme showed no inhibition on treatment with thiol specific reagents. This indicated that cysteine is present in close proximity of the lysine and is involved in the Isoindole Derivative formation but is not participating in the catalysis. These results established for the first time that one lysine residue present at the active site is required for the activity of dextransucrase.
Mikio Tsuzuki - One of the best experts on this subject based on the ideXlab platform.
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a stable monosubstituted Isoindole Derivative the crystal structure of 1 1 2 3 1h benzotriazol 1 yl 2 4 methylphenyl 2h Isoindole
Chemical & Pharmaceutical Bulletin, 1994Co-Authors: Ichiro Takahashi, Mikio Tsuzuki, Takashi Keumi, Hidehiko Kitajima, Shinzo Hosoi, Yoshisuke TsudaAbstract:1-(1, 2, 3-1H-benzotriazol-1-yl)-2-(4-methylphenyl)-2H-Isoindole (1a) is a stable Isoindole Derivative in the crystalline state. On the basis of the results of X-ray crystallographic analysis, this exceptional stability was explained as follows : the presence of a typical anti-parallel face-to-face stacking between Isoindole rings deprives the two reactive centers of an intermolecular approach.
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Studies on the double Mannich condensation reaction of o-phthalaldehyde with p-substituted anilines in the presence of 1,2,3-1H-benzotriazole
Heterocycles, 1994Co-Authors: Ichiro Takahashi, Mikio Tsuzuki, Hiroshi Yokota, Hidehiko KitajimaAbstract:The double Mannich condensation reaction in acetonitrile at room tempe- rature has been investigated. In the condensation reaction of o-phthal- aldehyde (1) with p-toluidine (2a; 1 equiv.) in the presence of 1,2,3- 1H-benzotriazole (Bt-H), the use of 3 equiv. of Bt-H afforded Bt-subs- tituted isoindoline Derivative (4a) exclusively for 8 h, and the use of 4 equiv. of Bt-H did for 4 h; further increment of reaction time induced the dissociation of Bt-H from (4a) to give 2H-Isoindole Derivative (5a). On the other hand, when methyl p-aminobenzoate (2b) was used ins- tead of (2a), the rate of the formation of isoindoline (4b) increased as the amount used of Bt-H was large (2 → 3 → 4 equiv.). Different from the 2-p-tolyl) counterpart, the increment of the reaction time did not induce the dissociation of Bt-H to afford 2H-Isoindole Derivative (5b)
