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[摘要]：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 Mg2+-binding sites in the catalytic center. (C) 2008 Published by Elsevier Inc. |
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