5-keto-D-gluconate production is catalyzed by a quinoprotein glycerol dehydrogenase, major polyol dehydrogenase, in gluconobacter species.
Acetic acid bacteria, especially Gluconobacter species, have been known to catalyze the extensive oxidation of sugar alcohols (polyols) such as D-mannitol, glycerol, D-sorbitol, and so on. Gluconobacter species also oxidize sugars and sugar acids and uniquely accumulate two different keto-D-gluconates, 2-keto-D-gluconate and 5-keto-D-gluconate, in the culture medium by the oxidation of D-gluconate. However, there are still many controversies regarding their enzyme systems, especially on D-sorbitol and also D-gluconate oxidations. Recently, pyrroloquinoline quinone-dependent quinoprotein D-arabitol dehydrogenase and D-sorbitol dehydrogenase have been purified from G. suboxydans, both of which have similar and broad substrate specificity towards several different polyols. In this study, both quinoproteins were shown to be identical based on their immuno-cross-reactivity and also on gene disruption and were suggested to be the same as the previously isolated glycerol dehydrogenase (EC 1.1.99.22). Thus, glycerol dehydrogenase is the major polyol dehydrogenase involved in the oxidation of almost all sugar alcohols in Gluconobacter sp. In addition, the so-called quinoprotein glycerol dehydrogenase was also uniquely shown to oxidize D-gluconate, which was completely different from flavoprotein D-gluconate dehydrogenase (EC 1.1.99.3), which is involved in the production of 2-keto-D-gluconate. The gene disruption experiment and the reconstitution system of the purified enzyme in this study clearly showed that the production of 5-keto-D-gluconate in G. suboxydans is solely dependent on the quinoprotein glycerol dehydrogenase.
Matsushita
Kazunobu
K
Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Japan. kazunobu@agr.yamaguchi-u.ac.jp
Fujii
Yoshikazu
Y
Ano
Yoshitaka
Y
Toyama
Hirohide
H
Shinjoh
Masako
M
Tomiyama
Noribumi
N
Miyazaki
Taro
T
Sugisawa
Teruhide
T
Hoshino
Tatsuo
T
Adachi
Osao
O
D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D005942:Gluconates / Q000378:metabolism*; D020576:Gluconobacter / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D013012:Sorbitol / Q000378:metabolism; D013401:Sugar Alcohol Dehydrogenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013402:Sugar Alcohols / Q000378:metabolism
D005942:Gluconates; D013402:Sugar Alcohols; D013012:Sorbitol; C093583:5-ketogluconic acid; D000429:Alcohol Oxidoreductases; D013401:Sugar Alcohol Dehydrogenases; C020672:glycerol dehydrogenase; C019641:alcohol dehydrogenase (acceptor); C014999:arabitol