Robrish S A, Fales H M, Gentry-Weeks C, Thompson J
Laboratory of Microbial Ecology, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892.
J Bacteriol. 1994 Jun;176(11):3250-6. doi: 10.1128/jb.176.11.3250-3256.1994.
Phosphoenolypyruvate-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 maintained under anaerobic conditions, but fermentation ceased immediately upon exposure of the cell suspension to air. Coincidentally, high levels of a phosphorylated derivative accumulated within the cells. Chemical and enzymatic analyses, in conjunction with data from 1H, 13C, and 31P nuclear magnetic resonance spectroscopy, established the structure of the purified compound as 6-O-phosphoryl-alpha-D-glucopyranosyl-(1-4)-D-glucose (maltose 6-phosphate). A method for the preparation of substrate amounts of this commercially unavailable disaccharide phosphate is described. Permeabilized cells of F. mortiferum catalyzed the phosphoenolpyruvate-dependent phosphorylation of maltose under aerobic conditions. However, the hydrolysis of maltose 6-phosphate (to glucose 6-phosphate and glucose) by permeabilized cells or cell-free preparations required either an anaerobic environment or addition of dithiothreitol to aerobic reaction mixtures. The first step in dissimilation of the phosphorylated disaccharide appears to be catalyzed by an oxygen-sensitive maltose 6-phosphate hydrolase. Cells of F. mortiferum, grown previously on maltose, fermented a variety of alpha-linked glucosides, including maltose, turanose, palatinose, maltitol, alpha-methylglucoside, trehalose, and isomaltose. Conversely, cells grown on the separate alpha-glucosides also metabolized maltose. For this anaerobic pathogen, we suggest that the maltose:phosphotransferase and maltose 6-phosphate hydrolase catalyze the phosphorylative translocation and cleavage not only of maltose but also of structurally analogous alpha-linked glucosides.
在死亡梭杆菌ATCC 25557细胞利用麦芽糖生长期间，磷酸烯醇丙酮酸依赖性麦芽糖：磷酸转移酶活性被诱导。在厌氧条件下维持的洗涤细胞能迅速代谢这种二糖，但当细胞悬液暴露于空气中时，发酵立即停止。与此同时，细胞内积累了高水平的磷酸化衍生物。化学和酶学分析，结合来自1H、13C和31P核磁共振光谱的数据，确定纯化化合物的结构为6-O-磷酸-α-D-吡喃葡萄糖基-(1-4)-D-葡萄糖（麦芽糖6-磷酸）。本文描述了一种制备这种商业上无法获得的二糖磷酸底物量的方法。死亡梭杆菌的透化细胞在有氧条件下催化麦芽糖的磷酸烯醇丙酮酸依赖性磷酸化。然而，透化细胞或无细胞制剂对麦芽糖6-磷酸（水解为葡萄糖6-磷酸和葡萄糖）的水解需要厌氧环境或向需氧反应混合物中添加二硫苏糖醇。磷酸化二糖异化的第一步似乎由一种对氧敏感的麦芽糖6-磷酸水解酶催化。先前在麦芽糖上生长的死亡梭杆菌细胞能发酵多种α-连接的糖苷，包括麦芽糖、松二糖、异麦芽糖、麦芽糖醇、α-甲基葡萄糖苷、海藻糖和异麦芽糖。相反，在单独的α-糖苷上生长的细胞也能代谢麦芽糖。对于这种厌氧病原体，我们认为麦芽糖：磷酸转移酶和麦芽糖6-磷酸水解酶不仅催化麦芽糖的磷酸化转运和裂解，还催化结构类似的α-连接糖苷的磷酸化转运和裂解。
