title: Crystal structure of maleylacetoacetate isomerase/glutathione transferase zeta reveals the molecular basis for its remarkable catalytic promiscuity.
abstract: 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.
authors.affiliation: The Biota Structural Biology Laboratory, St. Vincent's Institute of Medical Research, 41 Victoria Parade, Fitzroy, Victoria 3065, Australia.
authors.forename: G
authors.initials: G
authors.lastname: Polekhina
authors.forename: P G
authors.initials: PG
authors.lastname: Board
authors.forename: A C
authors.initials: AC
authors.lastname: Blackburn
authors.forename: M W
authors.initials: MW
authors.lastname: Parker
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019281:Dimerization; D005982:Glutathione Transferase / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013431:Sulfates / Q000378:metabolism; D019745:cis-trans-Isomerases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D013431:Sulfates; C407705:GSTZ1 protein, human; D005982:Glutathione Transferase; D019745:cis-trans-Isomerases; C021531:maleylacetoacetate isomerase