The Heterogeneity of Arginases in Rat Tissues

Arginase reactions in rat tissues were shown to be catalysed by three isoenzymes which can be separated by bidirectional electrophoresis on polyacrylamide gels. Anodic electrophoresis reveals a migrating band (isoenzyme I) present in all-non-hepatic tissues except submaxillary gland and a non-migrating band found in all tissues. The latter is resolved by cathodic electrophoresis into isoenzymes III (characteristic of liver and submaxillary gland) and a non-moving band (isoenzyme II), present in kidney, intestine and pancreas. Sequential electrophoresis, in the two directions, of mixture of liver and kidney extracts in the same gel columns separated all three isoenzymes. Differences in the solubilization properties, heat-sensitivity and substrate specificity of arginases from different tissues could be correlated with their electrophoretic behaviour. L-Canavanine could replace arginine as substrate in extracts of kidney but not of liver. Both kidney isoenzymes hydrolysed L-canavanine equally well, whereas isoenzyme III from submaxillary gland showed only very low activity. Antiserum against liver arginase interacted with the enzyme with submaxillary gland, but did not inactivate or adsorb arginase from kidney, intestine or pancreas. The distribution of arginase among 16 normal adult rat tissues is presented; the improved, sensitive, assay method was applicable to tissues containing as little as 0.1% of the hepatic activity.