Metabolism of Gentiobiose in Aerobacter aerogenes

Abstract

Cleavage of gentiobiose in cell extracts of gentiobiose-grown Aerobacter aerogenes was dependent on the presence of adenosine 5′-triphosphate (ATP). The enzymes that participate in the overall reaction were shown to be a β-glucoside kinase, which catalyzes the phosphorylation of gentiobiose with ATP to form gentiobiose monophosphate [6- O -phosphoryl-β- d -glucopyranosyl-(1 → 6)- d -glucose], and a phospho-β-glucosidase, which catalyzes the hydrolytic cleavage of gentiobiose monophosphate to form equimolar amounts of d -glucose and d -glucose 6-phosphate. Although the β-glucoside kinase was previously shown to catalyze the phosphorylation of many β-glucosides that serve as growth substrates (i.e., gentiobiose, cellobiose, cellobiitol, salicin, arbutin, methyl β- d -glucoside, and phenyl β- d -glucoside), mutant analysis and induction studies indicate that it functions only in the metabolism of gentiobiose, cellobiose, and cellobiitol.