Sprenger G A, Lengeler J W
KFA Jülich, Institut für Biotechnologie I, FRG.
J Gen Microbiol. 1988 Jun;134(6):1635-44. doi: 10.1099/00221287-134-6-1635.
In contrast to a previous report, strains of Klebsiella pneumoniae were found to take up and phosphorylate the disaccharide sucrose via the phosphoenolpyruvate-dependent carbohydrate phosphotransferase system (PTS). In addition to the two soluble and general components enzymeI and HPr of the PTS, a sucrose-specific enzymeIIScr (gene scrA), together with the enzymeIII, coded for by the gene crr, were needed for the vectorial phosphorylation of sucrose to generate intracellular sucrose 6-phosphate. This sugar phosphate is hydrolysed by a hydrolase (invertase, gene scrB) to generate glucose 6-phosphate and free fructose. The latter is converted to fructose 6-phosphate by an ATP-dependent fructokinase (gene scrK), an enzyme which is part of the sucrose and not of the fructose catabolic pathway. Analysis of different mutants of K. pneumoniae strain 1033, and of Escherichia coli K12 derivatives carrying R'scr plasmids isolated from K. pneumoniae, showed that the genes scrA, B, and K, together with a gene scrR for a repressor, form a genetic unit located on the chromosome of K. pneumoniae. These genes and the corresponding sucrose metabolic pathway are very similar to a previously described scr system encoded on plasmid pUR400 and found in other enteric bacteria.
与之前的一份报告不同，发现肺炎克雷伯菌菌株可通过磷酸烯醇丙酮酸依赖性碳水化合物磷酸转移酶系统（PTS）摄取蔗糖并使其磷酸化。除了PTS的两种可溶性通用成分酶I和HPr外，蔗糖特异性酶IIScr（基因scrA）与由基因crr编码的酶III一起，是蔗糖向细胞内蔗糖6-磷酸进行向量磷酸化所必需的。这种磷酸糖由水解酶（转化酶，基因scrB）水解生成葡萄糖6-磷酸和游离果糖。后者由依赖ATP的果糖激酶（基因scrK）转化为果糖6-磷酸，该酶是蔗糖分解代谢途径的一部分，而非果糖分解代谢途径的一部分。对肺炎克雷伯菌1033菌株的不同突变体以及携带从肺炎克雷伯菌分离的R'scr质粒的大肠杆菌K12衍生物的分析表明，基因scrA、B和K与阻遏物基因scrR一起，形成了一个位于肺炎克雷伯菌染色体上的遗传单位。这些基因以及相应的蔗糖代谢途径与先前描述的编码在质粒pUR400上并存在于其他肠道细菌中的scr系统非常相似。
