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首页> 外文期刊>Journal of bacteriology >Intracellular hexose-6-phosphate:phosphohydrolase from Streptococcus lactis: purification, properties, and function.
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Intracellular hexose-6-phosphate:phosphohydrolase from Streptococcus lactis: purification, properties, and function.

机译：乳酸链球菌的细胞内6-磷酸己糖：磷酸水解酶：纯化，性质和功能。

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An intracellular hexose 6-phosphate:phosphohydrolase (EC 3.1.3.2) has been purified from Streptococcus lactis K1. Polyacrylamide disc gel electrophoresis of the purified enzyme revealed one major activity staining protein and one minor inactive band. The Mr determined by gel permeation chromatography was 36,500, but sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a single polypeptide of apparent Mr 60,000. The enzyme exhibited a marked preference for hexose 6-phosphates, and the rate of substrate hydrolysis (at 5 mM concentration) decreased in the order, galactose 6-phosphate greater than 2-deoxy-D-glucose 6-phosphate greater than fructose 6-phosphate greater than mannose 6-phosphate greater than glucose 6-phosphate. Hexose 1-phosphates, p-nitrophenylphosphate, pyrophosphate, and nucleotides were not hydrolyzed at a significant rate. In addition, the glycolytic intermediates comprising the intracellular phosphoenolpyruvate potential in the starved cells (phosphoenolpyruvate and 2- and 3-phosphoglyceric acids) were not substrates for the phosphatase. Throughout the isolation, the hexose 6-phosphate:phosphohydrolase was stabilized by Mn2+ ion, and the purified enzyme was dependent upon Mn2+, Mg2+, Fe2+, or Co2+ for activation. Other divalent metal ions including Pb2+, Cu2+, Zn2+, Cd2+, Ca2+, Ba2+, Sr2+, and Ni2+ were unable to activate the enzyme, and the first four cations were potent inhibitors. Enzymatic hydrolysis of 2-deoxy-D-glucose 6-phosphate was inhibited by fluoride when Mg2+ was included in the assay, but only slight inhibition occurred in the presence of Mn2+, Fe2+, or Co2+. The inhibitory effect of Mg2+ plus fluoride was specifically and completely reversed by Fe2+ ion. The hexose 6-phosphate:phosphohydrolase catalyzes the in vivo hydrolysis of 2-deoxy-D-glucose 6-phosphate in stage II of the phosphoenolpyruvate-dependent futile cycle in S. lactis (J. Thompson and B. M. Chassy, J. Bacteriol. 151:1454-1465, 1982).
机译：已从乳酸链球菌K1中纯化了细胞内六糖六磷酸：磷酸水解酶（EC 3.1.3.2）。纯化酶的聚丙烯酰胺圆盘凝胶电泳显示一种主要的活性染色蛋白和一个次要的无活性条带。通过凝胶渗透色谱法测定的Mr为36,500，但是十二烷基硫酸钠-聚丙烯酰胺凝胶电泳显示表观Mr为60,000的单个多肽。该酶表现出对6-磷酸己糖的显着偏好，底物水解速率（在5 mM浓度下）依次降低，半乳糖6-磷酸大于2-脱氧-D-葡萄糖6-磷酸大于果糖6--。磷酸大于甘露糖6-磷酸大于葡萄糖6-磷酸。 1-磷酸己糖，对-硝基苯基磷酸酯，焦磷酸酯和核苷酸没有显着水解。另外，在饥饿的细胞中包含胞内磷酸烯醇丙酮酸潜力的糖酵解中间体（磷酸烯醇丙酮酸和2-和3-磷酸甘油酸）不是磷酸酶的底物。在整个分离过程中，己糖6-磷酸：磷酸水解酶被Mn2 +离子稳定，纯化的酶依赖于Mn2 +，Mg2 +，Fe2 +或Co2 +进行激活。其他二价金属离子（包括Pb2 +，Cu2 +，Zn2 +，Cd2 +，Ca2 +，Ba2 +，Sr2 +和Ni2 +）无法激活该酶，并且前四个阳离子是有效的抑制剂。当测定中包括Mg2 +时，氟化物抑制了2-脱氧-D-葡萄糖6-磷酸的酶水解，但是在Mn2 +，Fe2 +或Co2 +的存在下仅发生了轻微的抑制作用。 Mg2 +加氟化物的抑制作用被Fe2 +离子特异性和完全逆转。己糖6-磷酸：磷酸水解酶在乳酸链球菌依赖的磷酸烯醇丙酮酸依赖的无效周期的II期催化2-脱氧-D-葡萄糖6-磷酸的体内水解（J.Thompson和BM Chassy，J.Bacteriol.151 ：1454-1465，1982）。

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