THE REGULATION OF LIVER TRYPTOPHAN PYRROLASE ACTIVITY DURING THE DEVELOPMENT OF RANA CATESBIANA

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Abstract
1. Liver tryptophan pyrrolase activity was studied in embryonic, larval, and adult Rana catesbiana. Constitutive enzyme activity appeared after Shumway stage 22, disappeared during metamorphosis, and was again detected in appreciable amounts in the adult. 2. Substrate inducibility was positively correlated with constitutive enzyme activity. In no case was enzyme activity induced by substrate in the absence of detectable constitutive enzyme activity. 3. Culture of tadpoles in thyroxine solutions led to the suppression of enzyme activity. 4. L-histidine and hydrocortisone had no effect on liver tryptophan pyrrolase activity. 5. The appearance, during metamorphosis, of tryptophan pyrrolase activity was described. 6. The implications of these findings were discussed in terms of further experiments on the ontogeny of macromolecules.