Reaction catalyzed by 4-oxalomesaconate hydratase (4.2.1.83)

		=			+		H2O
	2-hydroxy-4-oxobutane-1,2,4-tricarboxylate	=		(1E,3E)-4-hydroxybuta-1,3-diene-1,2,4-tricarboxylate	+		H2O