FORMATION OF OXALIC ACID FROM SIDE CHAIN OF AROMATIC AMINO ACIDS IN RAT

1. 1. 14C from DL-[I-14C]tryptophan and DL[2-14C]tryptophan was incorporated into urinary oxalate of intact rats about the same extent, but DL-[3-14C]tryptophan did not label urinary oxalate. The incorporation of 14C from DL[2-14C]alanine into oxalate was only about 1 50 of that from DL-[2-14C]tryptophan. 2. 2. When sodium benzoate was given to rats together with either DL-[2-14C]-tryptophan or DL-[3-14C]tryptophan, the specific activities of the hippurate isolated from the urine were about equal, indicating that glyoxylate is not an intermediate in the major pathway by which oxalate arises from the side chain of tryptophan. 3. 3. The two terminal carbon atoms, but not the methylene carbon, of the side chain of [14C]tryptophan labeled oxalate when the amino acid was incubated with snake venom L-amino-acid oxidase [EC 1.4.3.2]. However, decarboxylation by auto-oxidation of the indolepyruvate thus formed was much more rapid than oxalate formation. 4. 4. DL-[2-14C]tyrosine and DL-[2-14C]phenylalanine also labeled oxalate when given to intact rats or after incubation with L-amino acid oxidase. 5. 5. The quantity of oxalate derived from the side chain moiety of the three aromatic amino acids tested was estimated to be less than 3% of the total oxalic acid excreted by the normal rat. © 1969.