Reaction catalyzed by diphthine synthase (2.1.1.98)

		+			=			+
	S-adenosyl-L-methionine	+		2-[(3S)-3-carboxy-3-(methylamino)propyl]-L-histidine-[translation elongation factor 2]	=		S-adenosyl-L-homocysteine	+		2-[(3S)-3-carboxy-3-(dimethylamino)propyl]-L-histidine-[translation elongation factor 2]