CARBON METABOLISM OF GLYCINE AND SERINE IN RELATION TO THE SYNTHESIS OF ORGANIC ACIDS AND A GUANINE DERIVATIVE.

Abstract

The metabolism of glycine or serine in aninmals alnd niicroorganisms has been well documented. The catabolism of glycine by way of glyoxylate is by far the 1mnost imiiportalnt pathway in mammalian tissues (9,10) and in microorganisms (2). Glyoxylate could be formiied from glycine either by the action of glycine oxidase (14) or by transamination (8,11). The metabolic conversion of serine to glycine and a 1-carhon uinit is reversible and has been denmonstrated to occur in animals (5) and plants (6,7,20). lHowever, in wheat leaves, glycine is converted preferentially to serine (16,17). The conversion of serine to glycine in vivo in wheat leaves proceeds very slowly (16,17). Wang and Waygood (18) investigated the conversion of glycine to sugars in wheat leaves and proposed a glyoxylate-serine pathway in wvhich serine occupies a key position as an essenitial internmediate. Rabson et al. (13) also have discussed the glycolate pathway for the production of precursors of hexoses. Recently, the role of serine in glycinie metabolism has been clearly demonstrated by Wang and Burris (16,17), and glyceric acid has been implicated as an intermediate between serine and hexoses (13,16,17,18). In additioni to the transformation of glycine or serine to hexoses, a considerable portion of either amino acid is utilized for the synthesis of a number of acidic compounds (15-18). The type of compotunds derived fromii these amino acids, besides glyceric and glycolic acids, had not been investigated fully, and the present communication deals with some of the fin(dinigs fromii a study of these compotnll(s.