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Thermokinetic Studies on the Activation of Arginase by Glycine
Author(s) -
Xie Xiuyin,
Wang Cunxin,
Wang Zhiyong
Publication year - 2010
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201090173
Subject(s) - chemistry , arginase , glycine , arginine , urea , substrate (aquarium) , ornithine , enzyme , reaction rate constant , hydrolysis , medicinal chemistry , inorganic chemistry , nuclear chemistry , biochemistry , amino acid , kinetics , oceanography , physics , quantum mechanics , geology
The activation of bovine liver arginase, which catalyzes the hydrolysis of L ‐arginine to L ‐ornithine and urea, by glycine was studied by thermokinetic methods at 37°C in 40 mmol·L −1 sodium barbiturate‐HCl buffer solution (pH 9.4). Results of this experiment indicate that an appropriate concentration of glycine can enhance the activity of arginase, and the relative activation rate reached its maximum value, 74%, when the concentration of glycine in reaction system was 1 mmol·L −1 and the initial concentration of arginine was 5 mmol·L −1 . With the increase of substrate concentration, the relative activation rate decreased in a definite glycine concentration. Michealis constant K m of reaction decreased from 5.53 to 3.31 mmol·L −1 and inhibition constant of product L ‐ornithine K p increased from 1.18 to 3.73 mmol·L −1 when glycine concentration was 1 mmol·L −1 . For these reasons one possible activation mechanism of arginase by glycine was suggested that the activation effect results from the competition of glycine and arginine to enzyme activity position. When one or two of the activity positions of arginase are occupied by glycine, it is propitious for the enzyme to complex with substrate and obstruct L ‐ornithine from combining with enzyme, and when all of the activity positions are occupied by glycine, the activation effect vanishs and the inhibition effect appears.