抄録
Tryptophan was found to be a factor that enhanced rat hepatic threonine dehydratase activity without resulting from increase in gluco-corticoid secretion. If rats were fed on tryptophan added diet prepared by adding 140mg/day tryptophan to 20g/day 20% casein diet, the resulting threonine dehydratase activity was about 1.5 times as much as that observed in rats fed 20% casein diet. If adrenalectomized rats were used, the similar results were obtained. In the case of hypophysectomized rats, however, about 4 times the activity was observed. This enormous increase in the activity was mostly prevented by growth hormone. This hormone was also effective in preventing the tryptophan-aided increase in threonine dehydratase activity of intact rats. Thyroxine was ineffective in preventing the activity increase. Either actinomycin S3 or puromycin treatment on rats disclosed that the tryptophan-aided activity increase was based on de novo synthesis of the enzyme through the translational step, not through the transcriptional one, of the protein biosynthesis.
Agrinine, histidine, isoleucine, leucine, methionine, phenylalanine, valine, and serine were ineffective in enhancing the hepatic threonine dehydratase activity.
