Enzymes of Arginine Metabolism in the Lizard Calotes Versicolor
Evolutionary transition from ureotelism to uricotelism in the animal kingdom is associated with the loss of a functional urea cycle and hence the ability to synthesize arginine (Campbell, 1973). Thus, while arginase is ubiquitously distributed in animals, one or more of the other enzymes of the urea cycle are absent in all the uricotelic animals that have been investigated (Brown and Cohen, 1960; Tamir and Ratner, 1963; Mora et al., 1965; Inokuchi et al., 1969; Kameyama and Miura, 1970; Reddy and Campbell, 1977). Arginase is usually regarded as a ureogenic enzyme, but ureogenesis can be a major function of arginase only in the ureotelic animals and not in the uricotelic animals. Knox and Greengard (1965) suggested that arginase functions in roles other than urea formation under situations where it exists without the other enzymes of the urea cycle.
KeywordsOrnithine Decarboxylase Urea Cycle Arginase Activity Arginine Metabolism Proline Oxidase
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