Reaction catalyzed by Isohexenylglutaconyl-CoA hydratase (4.2.1.57)

		=			+		H2O
	3-Hydroxy-3-(4-methylpent-3-en-1-yl)glutaryl-CoA	=		3-(4-methylpent-3-en-1-yl)pent-2-enedioyl-CoA	+		H2O