title: A pyrroloquinoline quinine-dependent membrane-bound d-sorbitol dehydrogenase from Gluconobacter oxydans exhibits an ordered Bi Bi reaction mechanism.
abstract: A membrane-bound pyrroloquinoline quinine (PQQ)-dependent D-sorbitol dehydrogenase (mSLDH) in Gluconobacter oxydans participates in the oxidation of D-sorbitol to L-sorbose by transferring electrons to ubiquinone which links to the respiratory chain. To elucidate the kinetic mechanism, the enzyme purified was subjected to two-substrate steady-state kinetic analysis, product and substrate inhibition studies. These kinetic data indicate that the catalytic reaction follows an ordered Bi Bi mechanism, where the substrates bind to the enzyme in a defined order (first ubiquinone followed by D-sorbitol), while products are released in sequence (first L-sorbose followed by ubiquinol). From these findings, we proposed that the native mSLDH bears two different substrate-binding sites, one for ubiquinone and the other for D-sorbitol, in addition to PQQ-binding and Mg(2+)-binding sites in the catalytic center.
authors.affiliation: State key Lab of Bioreactor Engineering, New World Institute of Biotechnology, East China University of Science and Technology, Mei-Long Road, Shanghai 200237, China.
authors.forename: Xue-Peng
authors.initials: XP
authors.lastname: Yang
authors.forename: Liu-Jing
authors.initials: LJ
authors.lastname: Wei
authors.forename: Jian-Bin
authors.initials: JB
authors.lastname: Ye
authors.forename: Bo
authors.initials: B
authors.lastname: Yin
authors.forename: Dong-Zhi
authors.initials: DZ
authors.lastname: Wei
mesh_terms: D002384:Catalysis; D002462:Cell Membrane / Q000201:enzymology*; D004789:Enzyme Activation; D004795:Enzyme Stability; D020600:Gluconobacter oxydans / Q000201:enzymology*; D007700:Kinetics; D007064:L-Iditol 2-Dehydrogenase / Q000737:chemistry*; D045542:PQQ Cofactor / Q000737:chemistry*; D013012:Sorbitol / Q000737:chemistry*; D013379:Substrate Specificity; D014451:Ubiquinone / Q000737:chemistry*
chemical_list: D014451:Ubiquinone; D013012:Sorbitol; D045542:PQQ Cofactor; D007064:L-Iditol 2-Dehydrogenase