Kinetics of inhibition of green crab (Scylla serrata) alkaline phosphatase by vanadate |
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Authors: | Chen Q X Zheng W Z Lin J Y Cai Z T Zhou H M |
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Affiliation: | Department of Biology, Xiamen University, Xiamen, 361005, People's Republic of China. |
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Abstract: | Green crab (Scylla serrata) alkaline phosphatase is a metalloenzyme that catalyzes the nonspecific hydrolysis of phosphate monoesters. The kinetics of inhibition of the enzyme by vanadate has been studied. The time course of the hydrolysis of p-nitrophenyl phosphate catalyzed by the enzyme in the presence of different Na3VO4 concentrations showed that, at each Na3VO4 concentration, the rate decreased with increasing time until a straight line was approached, the slopes of the straight lines being the same for all concentrations. The results suggest that the inhibition of the enzyme by Na3VO4 is a slow, reversible reaction with fractional residual activity. The microscopic rate constants were determined for the reaction of the inhibitor with the enzyme. As compared with Na2HPO4 (Ki = 0.95 mM), Na2HAsO4 (Ki = 1.10 mM), and Na2WO4 (Ki = 1.55 mM), the results suggest that Na3VO4 (Ki = 0.135 mM) is a considerably more potent inhibitor than other inhibitors. |
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