Thompson J, Chassy B M
J Bacteriol. 1981 Aug;147(2):543-51. doi: 10.1128/jb.147.2.543-551.1981.
Transport and metabolism of sucrose in Streptococcus lactis K1 have been examined. Starved cells of S. lactis K1 grown previously on sucrose accumulated [14C]sucrose by a phosphoenolpyruvate-dependent phosphotransferase system (PTS) (sucrose-PTS; Km, 22 microM; Vmax, 191 mumol transported min-1 g of dry weight of cells-1). The product of group translocation was sucrose 6-phosphate (6-O-phosphoryl-D-glucopyranosyl-1-alpha-beta-2-D-fructofuranoside). A specific sucrose 6-phosphate hydrolase was identified which cleaved the disaccharide phosphate (Km, 0.10 mM) to glucose 6-phosphate and fructose. The enzyme did not cleave sucrose 6'-phosphate(D-glucopyranosyl-1-alpha-beta-2-D-fructofuranoside-6'-phosphate). Extracts prepared from sucrose-grown cells also contained an ATP-dependent mannofructokinase which catalyzed the conversion of fructose to fructose 6-phosphate (Km, 0.33 mM). The sucrose-PTS and sucrose 6-phosphate hydrolase activities were coordinately induced during growth on sucrose. Mannofructokinase appeared to be regulated independently of the sucrose-PTS and sucrose 6-phosphate hydrolase, since expression also occurred when S. lactis K1 was grown on non-PTS sugars. Expression of the mannofructokinase may be negatively regulated by a component (or a derivative) of the PTS.
对乳酸链球菌K1中蔗糖的转运和代谢进行了研究。先前在蔗糖上生长的乳酸链球菌K1饥饿细胞通过磷酸烯醇丙酮酸依赖性磷酸转移酶系统（PTS）（蔗糖-PTS；Km，22μM；Vmax，191μmol转运min-1 g细胞干重-1）积累[14C]蔗糖。基团转位的产物是蔗糖6-磷酸（6-O-磷酸-D-吡喃葡萄糖基-1-α-β-2-D-呋喃果糖苷）。鉴定出一种特异性蔗糖6-磷酸水解酶，其将二糖磷酸（Km，0.10 mM）裂解为葡萄糖6-磷酸和果糖。该酶不裂解蔗糖6'-磷酸（D-吡喃葡萄糖基-1-α-β-2-D-呋喃果糖苷-6'-磷酸）。从在蔗糖上生长的细胞制备的提取物还含有一种ATP依赖性甘露糖激酶，其催化果糖转化为果糖6-磷酸（Km，0.33 mM）。在蔗糖上生长期间，蔗糖-PTS和蔗糖6-磷酸水解酶活性协同诱导。甘露糖激酶似乎独立于蔗糖-PTS和蔗糖6-磷酸水解酶进行调节，因为当乳酸链球菌K1在非PTS糖上生长时也会发生表达。甘露糖激酶的表达可能受到PTS的一个组分（或衍生物）的负调节。
