Roles of Conserved Residues of the Glycine Oxidase GoxA in Controlling Activity, Cooperativity, Subunit Composition, and Cysteine Tryptophylquinone Biosynthesis

摘要: GoxA is a glycine oxidase that possesses cysteine tryptophylquinone (CTQ) cofactor formed by posttranslational modifications are catalyzed modifying enzyme GoxB. It the second known to function as an oxidase, other being lysine ϵ-oxidase, LodA. All enzymes containing CTQ or tryptophan (TTQ) cofactors dehydrogenases. Kinetic analysis of revealed allosteric cooperativity for its substrate, but not O2. This first CTQ- TTQ-dependent exhibit cooperativity. Here, we show and homodimer stabilization strongly dependent on presence Phe-237. Conversion this residue, which Tyr in LodA, Ala eliminates destabilizes dimer. These mutations also significantly affect kcat Km values substrates. On basis structural modeling studies, mechanism Phe-237 exerts influence presented. Two active site residues, Asp-547 His-466, were examined shown site-directed mutagenesis be critical biogenesis. result compared with results similar studies structurally conserved residues enzymes. provide insight into roles specific active-site catalysis biogenesis, well describing interesting single residue can dictate whether exhibits cooperative behavior toward substrate.