Biosynthesis of arginine from canavanine and ornithine in kidney.

Borsook and Dubnoff (1, 2) and Bloch and Schoenheimer (3) have demonstrated that the amidine moiety of arginine is the precursor of the corresponding group of glycocyamine; in mammals this reaction is carried out primarily in the kidney. Fuld (4) has recently observed that the arginine-glycine transamidination reaction is reversible. By means of group transfer the high chemical potential of the amidine moiety is conserved. Since other metabolites containing the guanidino group occur in nature, it is of interest to determine whether they also participate in transamidination reactions. One such compound that might be investigated is canavanine, a naturally occurring amino acid which possesses a terminal guanidinoxyl group. In this paper data will be presented which show that in the presence of an enzyme from hog kidney canavanine donates an amidine group to ornithine, with the formation of arginine and canaline. Materials-L-Canavanine sulfate, L-ornithine dihydrochloride, L-arginine monohydrochloride, and beef liver arginase were purchased from the Nutritional Biochemicals Corporation. Preliminary experiments were carried out with canavanine isolated from jack bean meal as the thrice recrystallized flavianate; canavanine was regenerated from the flavianate with barium hydroxide. Analytical Methods-The ascending paper chromatographic procedure of Williams and Kirby was employed (5, 6). Paper chromatograms were sprayed with ninhydrin to detect primary amino groups or alkaline ferricyanide-nitroprusside to detect guanidino groups (6). Since canavanine does not react significantly with the Sakaguchi reagent, arginine could be determined calorimetrically in the reaction mixture with this reagent. The modified procedure of Albanese and Frankston (7) was employed. The components were mixed at 5”, and the optical densities at 540 rnp were read within 10 minutes with an Evelyn calorimeter. The stipulated hypochlorite concentration was met by using commercial Clorox, diluted 1:l.