The mitochondriogenesis and turnover of cytochrome c oxidase

The synthesis of cytochrome c oxidase in the liver mitochondria of the tadpole undergoing metamorphosis was studied in vivo and in vitro. The results obtained are as follows: 1) Cytochrome c oxidase was purified to immunological homogeneity from the adult bullfrog (Rana catesbeiana) liver. The purified enzyme had 13.5 nmol of heme a per mg of protein and was composed of nine polypeptides. The specific activity was 10.5.109 units/mol of heme a. 2) The antibody against the purified enzyme reacted with the mitochondrial extracts obtained from both the adult frog and the tadpole livers to form a single precipitin line, indicating that both the antigens were immunologically identical. 3) The amount of cytochrome c oxidase was found to increase consistently with the increasing enzyme activity during metamorphosis. 4) The rate of synthesis of cytochrome c oxidase was 2-3 times higher in the tadpole at the metamorphic climax than at the premetamorphic stage. 5) The rate of degradation of the enzyme in vivo was determined to be 13 h at the premetamorphic stage and 6 h at the metamorphic climax. 6) When the tadpoles were pretreated with cycloheximide, the synthesis of mitochondrial proteins was markedly inhibited in the tadpole liver at the premetamorphic stage but only a little at the metamorphic climax. 7) The competency of synthesis of cytochrome c oxidase was 3 times higher in the mitochondria isolated from the liver of the tadpole at the metamorphic climax than at the premetamorphic stage.