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首页> 外文期刊>Journal of bacteriology >Phosphoenolpyruvate and 2-phosphoglycerate: endogenous energy source(s) for sugar accumulation by starved cells of Streptococcus lactis.
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Phosphoenolpyruvate and 2-phosphoglycerate: endogenous energy source(s) for sugar accumulation by starved cells of Streptococcus lactis.

机译：磷酸烯醇丙酮酸和2-磷酸甘油酸：内源性能量源，用于乳酸链球菌饥饿细胞的糖积累。

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In the absence of an exogenous energy source, galactose-grown cells of Streptococcus lactis ML3 rapidly accumulated thiomethyl-beta-D-galactopyranoside (TMG) and 2-deoxyglucose to intracellular concentrations of 40 to 50 mM. Starved cells maintained the capacity for TMG uptake for many hours, and accumulation of the beta-galactoside was insensitive to proton-conducting ionophores (tetrachlorosalicylanilide and carbonylcyanide-m-chlorophenyl hydrazone) and sulfydryl group reagents including iodoacetate and N-ethylmaleimide. Fluorimetric analysis of glycolytic intermediates in extracts prepared from starved cells revealed (a) high intracellular levels of phosphoenolpyruvate (13 mM; PEP) and 2-phosphoglycerate (approximately 39 mM; 2-PG), but an absence of other metabolites including glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-diphosphate, and triosephosphates. The following criteria showed PEP (and 2-PG) to be the endogenous energy source for TMG accumulation by the phosphotransferase system: the intracellular concentrations of PEP and 2-PG decreased with concomitant uptake of TMG, and a close correlation was observed between maximum accumulation of the beta-galactoside and the total available concentration of the two intermediates; TMG accumulated as an anionic derivative, which after extraction and incubation with alkaline phosphatase (EC 3.1.3.1) formed the original analogue; fluoride inhibition of 2-phospho-D-glycerate hydrolyase (EC 4.2.1.11) prevented the conversion of 2-PG to PEP, and uptake of TMG by the starved cells was reduced by 80%; and the stoichiometric ratio [TMG] accumulated/[PEP] consumed was almost unity (0.93). In cells metabolizing glucose, all intermediates listed in (a) and (b) were found. Upon exhaustion of glucose from the medium, the metabolites in (b) were not longer detectable, while the intracellular concentrations of PEP and 2-PG increased to the levels previously observed in starved cells. The glycolytic intermediates in (b) are all in vitro heterotropic effectors of pyruvate kinase (adenosine 5'-triphosphate:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) from S. lactis ML3. It is suggested that the capacity of starved cells to maintain high intracellular concentrations of PEP and 2-PG is a consequence of decreased in vivo activity of this key regulatory enzyme of glycolysis.
机译：在没有外源能源的情况下，乳酸链球菌ML3的半乳糖生长细胞迅速积累了硫甲基-β-D-吡喃半乳糖苷（TMG）和2-脱氧葡萄糖，使其细胞内浓度达到40至50 mM。饥饿的细胞可以长时间维持TMG的摄取能力，β-半乳糖苷的积累对质子传导离子载体（四氯水杨基苯胺和羰基氰化物-间氯苯基-）和巯基试剂（包括碘乙酸盐和N-乙基马来酰亚胺）不敏感。从饥饿细胞制备的提取物中糖酵解中间体的荧光分析显示（a）高细胞内水平的磷酸烯醇丙酮酸（13 mM; PEP）和2-磷酸甘油酸酯（约39 mM; 2-PG），但缺少其他代谢物，包括葡萄糖6-磷酸盐，6-磷酸果糖，1,6-二磷酸果糖和磷酸三糖。以下标准显示，PEP（和2-PG）是磷酸转移酶系统TMG积累的内源性能源：PEP和2-PG的细胞内浓度随TMG的摄取而降低，并且观察到最大积累之间存在密切相关性β-半乳糖苷和两种中间体的总有效浓度; TMG以阴离子衍生物的形式积累，在提取并与碱性磷酸酶（EC 3.1.3.1）孵育后形成原始类似物;氟化物对2-磷酸-D-甘油酸水解酶的抑制作用（EC 4.2.1.11）阻止了2-PG向PEP的转化，饥饿细胞对TMG的吸收减少了80％。并且累积的化学计量比[TMG] /消耗的[PEP]几乎为1（0.93）。在代谢葡萄糖的细胞中，发现了（a）和（b）中列出的所有中间体。从培养基中耗尽葡萄糖后，（b）中的代谢物不再可检测，而细胞内PEP和2-PG的浓度增加到以前在饥饿细胞中观察到的水平。 （b）中的糖酵解中间体都是来自乳链球菌ML3的丙酮酸激酶（5'-三磷酸腺苷：丙酮酸2-O-磷酸转移酶，EC 2.7.1.40）的体外异向效应物。提示饥饿的细胞维持高细胞内PEP和2-PG浓度的能力是这种关键的糖酵解调节酶体内活性降低的结果。

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