Investigation of the structure and mechanism of a PQQ biosynthetic pathway component, PqqC, and a bioinformatics analysis of potential PQQ producing organisms

摘要: PQQ is an exogenous, tricyclic, quino-cofactor for a number of bacterial dehydrogenase reaction. It has also been proposed to play role as vitamin. The following work defined 144 bacteria species that contain the machinery form PQQ. formation based on conserved operon, pqqABCDEF, in Klebsiella pneumoniae. last enzymatic step biogenesis pathway catalyzed by PqqC and involves ring closure eight electron oxidation substrate AHQQ. Wild type (WT) various active site mutants have studied. asparagine alanine mutations at histidine 84 position supported published mechanism shown new H84 acid. This was anaerobic reactions, where H84A capable proceeding quinol intermediate anaerobically, but more conservative H84N mutation not. Aerobically, both were able Recent X-ray investigations variants Y175F (with bound), H154S bound) R179S/Y175S double mutant AHQQ show enzyme alternately closed, open conformation, respectively. Though does not characteristic closed conformation seen WT-PQQ structure, it still inititate with Using apo-glucose assay production, none are product formation. Spectrophotometric assays give insight into incomplete reactions being mutants. Active Y175F, H154N R179S quinoid anaerobically. Y175S reaction further forms anaerobically after forming quinoid. require O2 proceed intermediate. None preclude substrate/product binding. Indicating all cases, oxidative chemistry impeded because no can react fully quinone even presence O2. residues targeted proteinaceous core binding structure contributes activation.