Assay of fumarylacetoacetate fumarylhydrolase in human liver-deficient activity in a case of hereditary tyrosinemia.

The activity of human liver fumarylacetoacetate fumarylhydrolase (EC 3.7.1.2) has been determined with fumarylacetoacetate as substrate. The Km was found to be 1.3 mu mol/l. Subcellular fractionation showed localization of the enzyme in the particle-free supernatant (cytosol). ZnCl2, CuCl2 and p-chloromercuribenzoic acid had a marked inhibitory effect on the enzyme activity, but no inhibition was observed with a number of anions and substrate analogs. Fumarylacetoacetate fumarylhydorlase activity in liver tissue from a patient with hereditary tyrosinemia was found to be less 2% of the controls. The assay is applicable to 3 mg of liver tissue which may be obtained by needle biopsy.