PHOSPHOENOLPYRUVATE-DEPENDENT MALTOSE-PHOSPHOTRANSFERASE ACTIVITY IN FUSOBACTERIUM-MORTIFERUM ATCC-25557 - SPECIFICITY, INDUCIBILITY, AND PRODUCT ANALYSIS

Phosphoenolpyruvate-dependent maltose:phosphotransferase activity was induced in cells of Fusobacterium mortiferum ATCC 25557 during growth on maltose. The disaccharide was rapidly metabolized by washed cells m aintained under anaerobic conditions, but fermentation ceased immediat ely upon exposure of the cell suspension to air. Coincidentally, high levels of a phosphorylated derivative accumulated within the cells. Ch emical and enzymatic analyses, in conjunction with data from H-1, C-13 , and P-31 nuclear magnetic resonance spectroscopy, established the st ructure of the purified compound as -phosphoryl-alpha-D-glucopyranosyl -(1-4)-D-glucose (maltose 6-phosphate). A method for the preparation o f substrate amounts of this commercially unavailable disaccharide phos phate is described. Permeabilized cells of F. mortiferum catalyzed the phosphoenolpyruvate-dependent phosphorylation of maltose under aerobi c conditions. However, the hydrolysis of maltose 6-phosphate (to gluco se 6-phosphate and glucose) by permeabilized cells or cell-free prepar ations required either an anaerobic environment or addition of dithiot hreitol to aerobic reaction mixtures. The first step in dissimilation of the phosphorylated disaccharide appears to be catalyzed by an oxyge n-sensitive maltose 6-phosphate hydrolase. Cells of F. mortiferum, gro wn previously on maltose, fermented a variety of alpha-linked glucosid es, including maltose, turanose, palatinose, maltitol, alpha-methylglu coside, trehalose, and isomaltose. Conversely, cells grown on the sepa rate alpha-glucosides also metabolized maltose. For this anaerobic pat hogen, we suggest that the maltose:phosphotransferase and maltose 6-ph osphate hydrolase catalyze the phosphorylative translocation and cleav age not only of maltose but also of structurally analogous alpha-linke d glucosides.