NADPH-dependent L-sorbose reductase is responsible for L-sorbose assimilation in Gluconobacter suboxydans IFO 3291

Abstract

The NADPH-dependent L-sorbose reductase (SR) of L-sorbose-producing Gluconobacter suboxydans IFO 3291 contributes to intracellular L-sorbose assimilation. The gene disruptant showed no SR activity and did not assimilate the once-produced L-sorbose, indicating that the SR functions mainly as an L-sorbose-reducing enzyme in vivo and not as a D-sorbitol-oxidizing enzyme.

FIG. 1.

The metabolic pathway of d-sorbitol, l-sorbose, and their metabolites in Gluconobacter strains. *1, membrane-bound d-sorbitol dehydrogenase (2); *2, membrane-bound l-sorbose dehydrogenase (2); *3, NAD(P)-dependent l-sorbosone dehydrogenase (2); *4, NADPH-dependent l-sorbosone reductase (2); *5, NADPH-dependent l-sorbose reductase (2,11); *6, NAD-dependent d-sorbitol dehydrogenase (1).

FIG. 2.

Computer analysis of the sequences of upstream and downstream regions of the SR gene. B, BamHI; EI, EcoRI; EO, EcoO1091; EV, EcoRV; H, HindIII; S, SmaI.