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It is now well established that when high doses of Ltyrosine are consumed by guinea pigs or men, the phenolic group in the amino-acid is less readily metabolized if they subsist on a diet low in Lascorbic acid than if a diet containing sufficient of this compound to saturate the tissues is offered (cf. Sealock & Silberstein, 1940; Levine, Marples & Gordon, 1941 a, b). Evidence has, however, been produced (Painter & Zilva, 1947, 1948) which justifies the conclusion that this interaction between Lascorbic acid and L-tyrosine is a physiological response to an unusual situation and has no important bearing on normal nutrition. The part played by L-ascorbic acid is, nevertheless, of biochemical interest, and the in vitro experiments described in this communication throw some light on the problem. Pioneer work on the degradation ofthe molecule of L-tyrosine in the presence of animal tissue has been performed by Bernheim & Bernheim (1934), Krebs (1935) and Felix, Zorn & Dirr-Kaltenbach (1937). In these investigations the oxygen absorption and the evolution of ammonia techniques were employed. In the present work, as we were entirely concerned with the metabolism of the phenolic group of the molecule, we limited ourselves to the use of the Millon reaction only. Darby, DeMeio, Bernheim & Bernheim (1945) were unable to establish any difference in the rate of disappearance of the phenolic group of L-tyrosine when incubated with liver tissue from normal and from scorbutic guinea pigs for 4 hr. As will be seen from the following experiments, under our experimental conditions we had no difficulty in demonstrating that such a difference does exist, and we were in consequence in a position to investigate the problem in some detail.

biochemical journal

The influence of <scp>l</scp>-ascorbic acid on the disappearance of the phenolic group of <scp>l</scp>-tyrosine in the presence of guinea pig-liver suspensions

The influence of l-ascorbic acid on the disappearance of the phenolic group of l-tyrosine in the presence of guinea pig-liver suspensions