Three-dimensional structure of a purple lipoxygenase

Polyunsaturated fatty acid metabolism is governed primarily by two enzymes, prostaglandin H synthase and lipoxygenase. The crystal structure of the me tastable product-oxidized purple form of soybean lipoxygenase-3 was determi ned at 2.0 Angstrom resolution. The data reveal that the chromophore corres ponds to an iron-peroxide complex, a potential intermediate in the catalyze d reaction. A significant alteration of the iron site accompanies the forma tion of the complex. The structure, the first for a fatty acid-lipoxygenase complex, also reveals an unexpected mode of binding, and identifies amino acid residues that may play significant roles in catalysis, regio- and ster eoselectivity.