(33/50) A tightly bound quinone functions in the ubiquinone reaction sites of quinoprotein alcohol dehydrogenase of an acetic acid bacterium, Gluconobacter suboxydans.
Quinoprotein alcohol dehydrogenase (ADH) of acetic acid bacteria is a membrane-bound enzyme that functions as the primary dehydrogenase in the ethanol oxidase respiratory chain. It consists of three subunits and has a pyrroloquinoline quinone (PQQ) in the active site and four heme c moieties as electron transfer mediators. Of these, three heme c sites and a further site have been found to be involved in ubiquinone (Q) reduction and ubiquinol (QH2) oxidation respectively (Matsushita et al., Biochim. Biophys. Acta, 1409, 154-164 (1999)). In this study, it was found that ADH solubilized and purified with dodecyl maltoside, but not with Triton X-100, had a tightly bound Q, and thus two different ADHs, one having the tightly bound Q (Q-bound ADH) and Q-free ADH, could be obtained. The Q-binding sites of both the ADHs were characterized using specific inhibitors, a substituted phenol PC16 (a Q analog inhibitor) and antimycin A. Based on the inhibition kinetics of Q2 reductase and ubiquinol-2 (Q2H2) oxidase activities, it was suggested that there are one and two PC16-binding sites in Q-bound ADH and Q-free ADH respectively. On the other hand, with antimycin A, only one binding site was found for Q2 reductase and Q2H2 oxidase activities, irrespective of the presence of bound Q. These results suggest that ADH has a high-affinity Q binding site (QH) besides low-affinity Q reduction and QH2 oxidation sites, and that the bound Q in the QH site is involved in the electron transfer between heme c moieties and bulk Q or QH2 in the low-affinity sites. (+info)
(34/50) Gluconobacter japonicus sp. nov., an acetic acid bacterium in the Alphaproteobacteria.
(35/50) Screening of thermotolerant Gluconobacter strains for production of 5-keto-D-gluconic acid and disruption of flavin adenine dinucleotide-containing D-gluconate dehydrogenase.
(36/50) Purification, crystallization and preliminary X-ray analysis of L-sorbose reductase from Gluconobacter frateurii complexed with L-sorbose or NADPH.
(37/50) Production of glyceric acid by Gluconobacter sp. NBRC3259 using raw glycerol.
Gluconobacter sp. NBRC3259 converted glycerol to glyceric acid (GA). The enantiomeric composition of the GA produced was a mixture of DL-forms with a 77% enantiomeric excess of D-GA. After culture conditions, such as initial glycerol concentration, types and amounts of nitrogen sources, and initial pH, were optimized, Gluconobacter sp. NBRC3259 produced 54.7 g/l of GA as well as 33.7 g/l of dihydroxyacetone (DHA) from 167 g/l of glycerol during 4 d of incubation in a jar fermentor with pH control. GA production from raw glycerol samples, the main by-product of the transesterification process in the biodiesel production and oleochemical industries, was also evaluated after proper pretreatment of the samples. Using a raw glycerol sample with activated charcoal pretreatment, 45.9 g/l of GA and 28.2 g/l of DHA were produced from 174 g/l of glycerol. (+info)
(38/50) Microbial production of glyceric acid, an organic acid that can be mass produced from glycerol.
(39/50) Gluconobacter nephelii sp. nov., an acetic acid bacterium in the class Alphaproteobacteria.
(40/50) Use of a Gluconobacter frateurii mutant to prevent dihydroxyacetone accumulation during glyceric acid production from glycerol.
To prevent dihydroxyacetone (DHA) by-production during glyceric acid (GA) production from glycerol using Gluconobacter frateurii, we used a G. frateurii THD32 mutant, DeltasldA, in which the glycerol dehydrogenase subunit-encoding gene (sldA) was disrupted, but DeltasldA grew much more slowly than the wild type, growth starting after a lag of 3 d under the same culture conditions. The addition of 1% w/v D-sorbitol to the medium improved both the growth and the GA productivity of the mutant, and DeltasldA produced 89.1 g/l GA during 4 d of incubation without DHA accumulation. (+info)
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