[Determination of the KM-value of the fumarase (E.C. 4.2.1.2) with bencyclan-hydrogenfumarate as the substrate (author's transl)].

The Michaelis-Menten constant for fumarase (E.C. 4.2.1.2) has been determined by measuring the enzyme activity by the spectrophotometric method of Racker, which depends on the formation or disappearance of the double bond of fumaric acid. When using Na2-fumarate or bencyclan hydrogenfumarate (Fludilat), respectively, as a substrate, a KM-value of 1.3 X 10(-3) M was found for both substances. In a linked assay where the formation of NADH in the reaction of fumarate leads to malate leads to oxaloacetate was used as a parameter for the reaction rate, a KM-value of 1.35 X 10(-3) M was found.