Metabolic Pathway for 2-Keto-L-gulonic Acid Formation in Gluconobacter melanogenus IFO 3293

Abstract

The L-sorbosone pathway for 2-keto-L-gulonic acid (2KGA) formation from L-sorbose in Gluconobacter melanogenus IFO 3293 was confirmed. L-Sorbose dehydrogenase, which catalyzes the conversion of L-sorbose to L-sorbosone, was found in the membrane fraction of the microorganism, and L-sorbosone dehydrogenase in the cytosol fraction. The latter enzyme requires NAD or NADP as a cofactor.
2KGA was reduced to L-idonic acid by 2KGA reductase, but L-idonic acid was re-oxidized to 2KGA by membrane-bound L-idonate dehydrogenase.