Yates E, Gao L, Woodcock N, Parsons N, Cole J, Smith H
School of Biosciences, University of Birmingham, United Kingdom.
Int J Med Microbiol. 2000 Dec;290(7):627-39. doi: 10.1016/S1438-4221(00)80012-0.
The reason for stimulation by lactate of metabolism of gonococci growing in a medium containing glucose, which enhances pathogenicity by increasing growth rate, lipopolysaccharide (LPS) synthesis and protein formation, has been investigated. Tricine dodecylpolyacrylamide gel electrophoresis (SDS-PAGE) and thin layer chromatography (TLC) on homogenates of gonococci grown in this medium with [14C]lactate showed that lactate carbon was preferentially incorporated into lipid and LPS. Nuclear magnetic resonance (NMR) spectroscopy on lipid extracted from gonococci grown in the glucose containing medium with [13C]lactate showed that lactate carbon was incorporated into fatty acid moieties and not into ethanolamine or glycerol moieties. In contrast, NMR on lipid from gonococci grown with [13C]glucose indicated glucose carbon in both moieties. When unlabelled lactate was added, lipid synthesis from [l3C]glucose was stimulated and small amounts of different fatty acids were formed. The NMR data shows that gluconeogenesis from lactate carbon does not occur in the presence of glucose, suggesting that lactate is used solely for rapid production, via pyruvate, of acetyl CoA, the precursor not only for fatty acid synthesis but also for the constituents and products of the citric acid cycle, including ATP. The rapid formation of a high level of acetyl CoA is the probable reason for the stimulation of metabolism and oxygen uptake by lactate. 14C label on LPS was detected in its fatty acids. Most proteins that stained with silver in tricine SDS-PAGE were not significantly labelled by [14C]lactate in the glucose-containing medium. Two of three appreciably labelled proteins were identified by N-terminal sequencing as GroEL and porin 1B, and one of the two less labelled proteins was similar to peroxiredoxin type proteins. There were no signs of specific induction of these proteins by lactate and their labelling was consistent with fatty acids in attached lipid.
乳酸对在含葡萄糖培养基中生长的淋球菌代谢具有刺激作用，该作用通过提高生长速率、脂多糖（LPS）合成和蛋白质形成来增强致病性，其原因已得到研究。用[14C]乳酸在这种培养基中培养的淋球菌匀浆进行的Tricine十二烷基聚丙烯酰胺凝胶电泳（SDS-PAGE）和薄层色谱（TLC）显示，乳酸碳优先掺入脂质和LPS中。用[13C]乳酸在含葡萄糖培养基中培养的淋球菌提取的脂质进行核磁共振（NMR）光谱分析表明，乳酸碳掺入脂肪酸部分，而不掺入乙醇胺或甘油部分。相比之下，用[13C]葡萄糖培养的淋球菌脂质的NMR表明，两种部分都有葡萄糖碳。当添加未标记的乳酸时，[l3C]葡萄糖的脂质合成受到刺激，并形成少量不同的脂肪酸。NMR数据表明，在有葡萄糖存在的情况下，乳酸碳不会发生糖异生，这表明乳酸仅通过丙酮酸用于快速生成乙酰辅酶A，乙酰辅酶A不仅是脂肪酸合成的前体，也是柠檬酸循环的成分和产物（包括ATP）的前体。乙酰辅酶A快速形成高水平可能是乳酸刺激代谢和氧气摄取的原因。在LPS的脂肪酸中检测到14C标记。在含葡萄糖培养基中，Tricine SDS-PAGE中用银染色的大多数蛋白质未被[14C]乳酸显著标记。通过N端测序鉴定出三个明显标记的蛋白质中的两个为GroEL和孔蛋白1B，两个标记较少的蛋白质中的一个与过氧化物酶类型的蛋白质相似。没有迹象表明这些蛋白质被乳酸特异性诱导，并且它们的标记与附着脂质中的脂肪酸一致。
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