Incorporation of C 14 From Carboxyl-Labeled dl -Alanine Into the Proteins of Liver Slices

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Abstract
Studies of protein formation in liver slices, as measured by the incorporation of carboxyl-labeled alanine, are descr. The alanine was prepared by the Strecker synthesis with modifications appropriate for use of small amts. of radioactive HCN. The HCN was generated from KCN made by the method of Kramer and Kistiakowsky with certain changes. Preliminary expts., in which relatively large amts. of nonradioactive dl-alanine were added to a. tagged hydrolysate and the alanine crystallized 3 times, indicate that a large percentage of the activity in the hydrolysate could be accounted for as alanine. Small amts. of activity were found when similar crystallizations were conducted with l(+)-glutamic acid and with dl-aspartic acid. No activity was found in glycine. Although the pathway by which alanine is incorporated into the proteins of liver slices is obscure, it was found that it could not occur in the absence of O2. This finding is compatible with theories of protein synthesis which postulate coupling with energy-yielding reactions.