General discussion

GENERAL DISCUSSION CHARLES A. NICHOL" I would like to make a comment with regard to the specificity of tryptophan as an inducer of tryptophan pyrrolase. Studies by Dr. Rosen and Dr. Milholland (Fed. Prec. 21, 237, 1962) indicate that analogues of tryptophan including D-tryptophan, acetyl-L-tryptophan, indole, D, L-5-OH-tryptophan and serotonin when given intraperitoneally can increase (50-300 per cent) the activity of both tryptophan pyrrolaso and tyrosine transaminase in the liver of adrenalectomized rats. To gain further information on the mechanism of the induction of tryptophan pyrrolase, Puromycin and also ethionine were used as inhibitors of protein synthesis, in order to separate the response of this enzyme into its two components, activation and synthesis of new protein. The major portion of the response of tryptophan pyrrolase to cortisol was mediated by synthesis of new enzyme. However, the substrate (tryptophan) induced increase in activity of this enzyme in adrenalectomized and hypophysectomized rats was found to involve mainly (about 75 per cent) enzyme activation.

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