The utilization of some phenylpyruvic acids for growth in the rat.

Throughout, the normal pathway of the metabolism of most amino acids there is a constant loss or int’erchange of amino groups. In the process of deamination keto acids, rather than hydroxy acids, appear to be the chief products (1, 2). In this manner a va.riet)y of keto acids are continuously being generated in the animal body. The fate of these naturally occurring carbonyl compounds is of particular interest in their relation to the promotion of growth. The keto analogue has been reported as capable of substit’ut ing for the amino acid in the case of methionine (3), tryptophan (4), histidine (Z), leucine, isoleucine (6), and phenylalanine (7). Reports concerning the remaining essential amino acids have not appesred in the lit.erature. Tyrosine, usually considered as a non-essential amino acid for the growth of the white rat, has been shown by Womack and Rose (8) to be capable of replacing about one-half of the phenylalanine requirement of the growing rat. Since tyrosine is non-essential in the presence of sufficient phenylalanine, the growth effect of the analogues has never been established. In an earlier paper (9) it has been shown that when suboptimal am0unt.s of phenylalanine are incorporated in an amino acid mixture, otherwise adequate for the white rat, the additional requirement for phenylalanine is met equally well with D-, L-, or rm-tyrosine, as evidenced by normal growth. By means of this technique we have studied the utilization of the keto analogue of tyrosine, p-hydroxyphenylpyruvic acid, for growth in the rat. The keto analogue of phenylalanine, phenylpyruvic acid, has been stated in a review by Rose (7) to be capable of promoting growth in the absence of phenylalanine. As far as we are aware, no experimental data were reported.