Three-dimensional structure of galactose oxidase: an enzyme with a built-in secondary cofactor.

摘要: Galactose oxidase is a copper-containing enzyme, which catalyses stereospecific oxidation of primary alcohols. The three-dimensional structure the enzyme has been determined in this study by X-ray crystallography at high resolution.The molecule almost entirely composed β-structures and consists three domains. arrangement 28 β-strands second domain particular interest, having seven four-stranded antiparallel β-sheets with pseudo-sevenfold symmetry. copper site square-pyramidal coordination two histidines, one tyrosine exogenous ligand equatorial sites another axial site. most intriguing structural feature covalent bond between CIµ1 Tyr-272, ligands, Sγ Cys-228. This unexpected thioether bond, Trp-290 stacked above it, strongly supports presence free radical as ‘built-in’ secondary cofactor.Calculation molecular surface shows, small pocket suggests substrate-binding model, can explain substrate specificity. A model for catalytic mechanism, involving basic tryptophan, also proposed.