Amino acid incorporation and biotin deficiency.

Biotin deficiency in chicks has been reported to result in a marked decrease in the synthesis of albumin and in the activity of amylase (3). Kritsman, Konikova, and Yukhnovskaya (4) observed that the incorporation of methionine-S3s into the proteins of biotin-deficient rats was reduced as compared to the normal animals. Studies in vitro gave similar results; also, the addition of biotin to the system increased the amino acid incorporation into the protein. In studies with Streptococcus lactis, Sund, Ravel, and Shive (5) found that the ornithine transcarbamylase activity of biotin-deficient cells could be restored to normal by biotin only when a mixture of amino acids, glucose, and the like was included in the reactivation medium. This and other evidence (6) suggested that in some way biotin was involved in the synthesis de novo of the enzyme. In our studies (7) on the intracellular distribution of biotin-COOH-Cl4 in rat and chick livers we observed that 40 to 50% of the labeled vitamin in the homogenate was found in the soluble cell fraction and that most of this biotin was associated with the pH 5 fraction. On the other hand, the supernatant fraction from biotin-deficient livers contained very little biotin. In view of this, we were led to investigate the role of the vitamin in protein synthesis. The results of studies in vivo and in vitro on the incorporation of labeled amino acids into proteins are given in this paper