Comparative studies of waste nitrogen metabolism in Amphibia

Abstract

Some properties of arginase in the liver of Rana temporaria were studied. The crude enzyme has a pH optimum of 9.55, is activated by manganese ions, and shows maximum activity only at substrate concentrations of about 0.3 [image]. These properties are similar to those of rat-liver arginase. Arginase activity in the liver of Xenopus laevis is even higher than in Rana temporaria, whether expressed in units per gram of liver or per gram body weight. Kidney glutaminase activity in Xenopus is only slightly higher than in Rana. Many L-amino acids are deaminated much more rapidly in Xenopus kidney than in that of Rana. Kidney D-amino acid oxidase activity in Rana is higher than in Xenopus.