NEW METABOLIC PRODUCTS OF L-CITRULLINE AND L-HOMOARGININE

Abstract

Several clinical conditions associated with hyperammonemia are also characterized, in part, by elevated serum and urine levels of citrulline (C), homocitrulline (HC), and homoarginine (HA). Our previous studies on 14C-ureido-HC revealed that HC was converted by rats and mice, and, in vitro, by L-amino acid oxidase to a cyclic derivative (Fed. Proc. 35:1478, 1976). We now report mass spectrometric data which indicate that an L-amino acid oxidase product of (C) is also cyclic.L-HA is also converted by rats and mice, and in vitro, by amino-acid oxidase to yet another unreported compound. The HA metabolite does not react with ninhydrin but does form a hydrazone with dinitrophenylhydrazine, and thus, may be a straight chain molecule. Enzymatic studies suggest that these α-keto derivatives are formed, in vivo, by transamination reactions.These newly discovered metabolites may represent significant pathways for the disposal of HC, C, and HA in clinical situations where they accumulate.