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Regulation of the hydrolytic and transfer activities of gamma-glutamyl transpeptidase.
- Source :
-
Life sciences [Life Sci] 1990; Vol. 46 (19), pp. 1343-8. - Publication Year :
- 1990
-
Abstract
- The activity of gamma-glutamyl transpeptidase was inhibited and stimulated by hippurate with and without acceptor molecules, respectively. Substrate activation was observed when acceptor molecules was not present but the activation was disappeared by the addition of hippurate. When glutamine was absent the inhibition degree of hippurate at pH 8.0 was greater than at pH 7.0, whereas in the presence of both hippurate and glutamine the results were opposed. These show a possibility that glutaminase is activated by hippurate under the condition of physiological pH. The activation of glutaminase by hippurate was also confirmed directly. The inhibition degree of transfer activity by glutamine was increased along the increase of acceptor concentration only in the presence of hippurate. Gamma-Glu-Phe-Gly satisfying prerequisites for donors doesn't act as a substrate, which shows that L-gamma-glutamyl-p-nitroanilide itself hardly acts as an acceptor. This contradicts to an idea that substrate activation caused by autotranspeptidation. The change of apparent Km and Vmax according to the change of pH in the presence of hippurate was different from that in the presence of acceptors. This shows a possibility that the active site on small subunit is inhibited and the latent active site in large subunit is exposed by the interaction of hippurate to the enzyme.
- Subjects :
- Animals
Cattle
Enzyme Activation drug effects
Glutamates biosynthesis
Glutamic Acid
Glutaminase metabolism
Glutamine pharmacology
Hippurates pharmacology
Hydrogen-Ion Concentration
Hydrolysis
Kidney enzymology
Kinetics
Maleates pharmacology
Substrate Specificity
gamma-Glutamyltransferase antagonists & inhibitors
gamma-Glutamyltransferase metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0024-3205
- Volume :
- 46
- Issue :
- 19
- Database :
- MEDLINE
- Journal :
- Life sciences
- Publication Type :
- Academic Journal
- Accession number :
- 1971703
- Full Text :
- https://doi.org/10.1016/0024-3205(90)90333-m