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

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Abstract
The rate of disappearance of the phenolic group of L-tyrosine in the presence of suspensions of livers from normal or from scorbutic guinea pigs was investigated over periods up to 10 hrs. The reaction was found to be slow and proceeded at a higher rate when suspensions from livers of normal animals were used. Glycyl-L-tyrosine could replace the L-tyrosine as substrate. Suspensions of livers from scorbutic guinea pigs injd. with 25 mg. of L-ascorbic acid 18 hrs. before death functioned like those from normal animals. The accelerating effect of graded quantities (0.5-10 mg.) of L-ascorbic acid was investigated in the presence of liver suspensions from normal and scorbutic animals using L-tyrosine and glycyl-L-tyrosine as substrates. The addition of 2.5 mg. of the acid was found to produce the optimum acceleration. No L-ascorbic acid was used up in the reaction. D-Glucoascorbic acid, which is antiscorbutic ally inactive, accelerated the above degradation in vitro to the same extent as equivalent amts. of L-ascorbic acid.