Maleylacetoacetate isomerase (MAAI), a key enzyme in the metabolic degradation of phenylalanine and tyrosine, catalyzes the glutathione-dependent isomerization of maleylacetoacetate to fumarylacetoacetate. Deficiencies in enzymes along the degradation pathway lead to serious diseases including phenylketonuria, alkaptonuria, and the fatal disease, hereditary tyrosinemia type I ...
Maleylacetoacetate isomerase (MAAI), a key enzyme in the metabolic degradation of phenylalanine and tyrosine, catalyzes the glutathione-dependent isomerization of maleylacetoacetate to fumarylacetoacetate. Deficiencies in enzymes along the degradation pathway lead to serious diseases including phenylketonuria, alkaptonuria, and the fatal disease, hereditary tyrosinemia type I. The structure of MAAI might prove useful in the design of inhibitors that could be used in the clinical management of the latter disease. Here we report the crystal structure of human MAAI at 1.9 A resolution in complex with glutathione and a sulfate ion which mimics substrate binding. The enzyme has previously been shown to belong to the zeta class of the glutathione S-transferase (GST) superfamily based on limited sequence similarity. The structure of MAAI shows that it does adopt the GST canonical fold but with a number of functionally important differences. The structure provides insights into the molecular bases of the remarkable array of different reactions the enzyme is capable of performing including isomerization, oxygenation, dehalogenation, peroxidation, and transferase activity.
Related Citations:
Characterization and chromosome location of the gene GSTZ1 encoding the human Zeta class glutathione transferase and maleylacetoacetate isomerase Blackburn, A.C., Woollatt, E., Sutherland, G.R., Board, P.G. (1998) Cytogenet Cell Genet 83: 109
Glutathione transferase Zeta catalyses the oxygenation of the carcinogen dichloroacetic acid to glyoxylic acid Tong, Z., Board, P.G., Anders, M.W. (1998) Biochem J 331: 371
Organizational Affiliation:
The Biota Structural Biology Laboratory, St. Vincent's Institute of Medical Research, 41 Victoria Parade, Fitzroy, Victoria 3065, Australia.
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