Analysis of sorbitol metabolism in genus Gluconobacter.

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It is revealed that D-sorbitol, not L-sorbose, is the inducer of sldSLC, the gene for FAD-sorbitol dehydrogenase (SLDH), yielding L-sorbose from D-sorbitol. The obtained results were published.PQQ-glycerol dehydrogenase (GLDH), yielding also L-sorbose from D-sorbitol, connects efficiently to cytochrome bo 3 terminal oxidase and higher energy conservation ratio, thus it plays a major role in L-sorbose production. On the other hand, FAD-SLDH linked preferably to the cyanide-insensitive terminal oxidase, CIO. The obtained results were published.The SboA enzyme expressed and purified from an Escherichia coli transformant showed NADPH-dependent L-sorbose reductase (NADPH-SR) activity. The obtained results are published. Now the enzyme is served for structural analysis by x-ray crystallographyReverse transcription-PCR experiments indicated that sboRA comprises an operon. It is expected that SboR is a transcriptional regulator which binds with L-sorbose. SboR was expressed and purified from E. coli transformant and used for gel-shift assay with the DNA fragment containing the promoter-operator region for sboRA, however, we failed to demonstrate that SboR has an ability to bind the DNA fragment with or without L-sorbose. The obtained results were published.The gene for FAD-gluconate dehydrogenase (GADH), yielding 2-ketogluconic acid from D-gluconate, was cloned and sequenced.For easy measurement for 5-ketogluconate (5KGA) and 2-ketogluconate (2KGA), genes for 5KGA reductase and 2KGA reductase were cloned and expressed in E. coli, Both enzyme preparations were easily obtained from E. coli transformants after one column chromatography.