Membrane-Bound Dehydrogenases of Acetic Acid Bacteria

Abstract

One of the major key features of acetic acid bacteria is their strong oxidation ability of alcohols and sugars, resulting in quantitative production of oxidized compounds. Respiratory chains consisting of ubiquinone, terminal ubiquinol oxidase, and several primary membrane-bound dehydrogenases are responsible for this unique ability. Here, we describe recent progress in the understanding of enzymatic and molecular properties and biogenesis of the membrane-bound dehydrogenases, such as pyrroloquinoline quinone-dependent alcohol dehydrogenase–cytochrome complex, and recent findings on new membrane-bound dehydrogenases. Quinate oxidation by quinate dehydrogenase (QDH) of acetic acid bacteria is a key agent in the vitro shikimate production process composed of the membranes containing QDH and 3-dehydroquinate dehydratase and NADP+-dependent shikimate dehydrogenase. The addition of a catalytic amount of NADP+ and an NADPH-regeneration system drive the process forward to produce shikimate with almost 100 % yield. The pentose oxidation respiratory chain produces 4-keto-d-arabonate or 4-keto-d-ribonate, depending on the substrate. Novel three different membrane-bound enzymes are indicated: d-aldopentose 4-dehydrogenase, 4-keto-d-aldopentose 1-dehydrogenase, and d-pentonate 4-dehydrogenase.