Enzymatic transamination reactions involving arginine and ornithine.

Recent research has resulted in considerable modification of the earlier concept that enzymatic transamination was limited to reactions between alanine, aspartate, glutamate, and their or-keto analogues. Reactions leading to the reversible amination of the cY-keto analogues of many of the natural amino acids have been described (l-5), and there is also evidence that aldehyde groups may participate in transamination (6-9). It has been reported that incubation of ar-ketoglutarate and arginine with crude liver and kidney preparations resulted in glutamate formation (2). The presence of arginase in these preparations was apparently not investigated, and the participation of arginine itself in transamination remains to be demonstrated. Transamination between pyruvate and ornithine in liver preparations yielding alanine has also been described (10). Although no evidence concerning the fate of the ornithine carbon chain in the liver system was obtained, a transamination reaction between ornithine and cu-ketoglutarate catalyzed by extracts of Neurospora crassa has been found to yield glutamate and glutamic-r-semialdehyde (7). The present report describes an investigation of transamination reactions catalyzed by liver preparations between glutamine and the ar-keto analogues of arginine (a-keto-&guanidinovaleric acid) and nitroarginine (OLketo-&nitroguanidinovaleric acid). In the course of this study, transamination between ornithine and a-ketoglutarate yielding glutamate and glutamic-r-semialdehyde was observed. Ornithine was subsequently found to transaminate with glyoxylate, oc-ketobutyrate, and a number of other cy-keto acids to yield glutamic-r-semialdehyde and the corresponding amino acids. This paper also reports studies on the growth response of rats to a-keto-&guanidinovaleric acid.