Reaction catalyzed by 2-ketoarginine methyltransferase (2.1.1.243)

		+			=			+
	S-adenosyl-L-methionine	+		5-guanidino-2-oxopentanoate	=		S-adenosyl-L-homocysteine	+		5-guanidino-3-methyl-2-oxopentanoate