The metabolism of glycine by folic acid-deficient chick liver homogenates.

Recent work has made it clear that folic acid is intimately concerned in glycine metabolism. It was shown that a deficiency of glycine produced by feeding sodium benzoate (1) was partially prevented by this vitamin. Likewise, growth in rats fed toxic levels of glycine ir improved by folic acid (2, 3). Holland and Meinke (4) have found that both glycine and folic acid seem to improve the ability of such organisms as Streptococcus faecalis to grow with very low levels of serine in the medium. Likewise there is some evidence that porphyrin metabolism is influenced by folic acid both in animals and in microorganisms (1, 5, 6). It is known that the ar-methylene carbon of glycine is incorporated into porphyrin (7) and that the carboxyl carbon of glycine does not appear in the porphyrin portion of the hemoglobin molecule (8). These experiments taken together suggest that folic acid is necessary for the breakdown of glycine into a l-carbon intermediate or incorporation of this carbon into serine and other substances such as purines, pyrimidines, and porphyrin. Evidence that folic acid is concerned in the production of pyrimidines and purines has been reviewed in a recent paper by Prusoff et al. (9), but direct evidence that the vitamin action is exerted through its influence on glycine metabolism is lacking. It seemed likely to us that the best approach to the solution of this problem was through the use of C4-labeled glycine. The results of the first of these studies is presented here. For the present experiments chicks were used, since it is possible to induce an uncomplicated dietary deficiency of folic acid in this species. The radioactive glycine’ used contained Cl4 in the carboxyl group and exhibited an activity of about 10 PC. per mg.