Abstract
The distribution of pyridine nucleotide transhydrogenase was examined in various tissues, chiefly in skeletal muscle, of 21 species of marine and freshwater fishes. The activity of this enzyme was detected irrespective of fish species or of source tissues. The activity in the muscle of several species of fishes such as yellowtail and lizard fish was particularly high. The D. D activity of this enzyme generally was several times stronger than the T. D activity in the muscle. It was noticed that the piscine enzyme, unlike that of mammalian origin, is easily solubilized from muscle prefrozen for several days below -20°C. As for the intracellular distri-bution of the enzyme activity, it was found that it is localized in the mitochondrial fraction as it is in mammals.
