Evidence by GC-MS that lysine is an arginase-catalyzed metabolite of homoarginine in vitro and in vivo in humans

l-Homoarginine (hArg) is biosynthesized from l-arginine (Arg) and l-lysine (Lys) by arginine:glycine amidinotransferase (AGAT). AGAT also catalyzes the formation of guanidinoacetate (GAA) from Arg and glycine (Gly). GAA is converted to creatine (N-methyl guanidinoacetate) by guanidinoacetate N-methyl-transferase (GAMT). Low circulating and excretory concentrations of hArg are associated with worse cardiovascular outcome and mortality. hArg is a...