Bagramyan Karine, Mnatsakanyan Nelli, Trchounian Armen
Department of Biophysics of the Biological Faculty, Yerevan State University, 1 Alex Manougian Str., 375049, Yerevan, Armenia.
Biochem Biophys Res Commun. 2003 Jun 27;306(2):361-5. doi: 10.1016/s0006-291x(03)00967-7.
Escherichia coli growing on glucose under anaerobic conditions at slightly alkaline pH carries out a mixed-acid fermentation resulting in the production of formate among the other products that can be excreted or further oxidized to H(2) and CO(2). H(2) production is largely dependent on formate dehydrogenase H and hydrogenases 3 and 4 constituting two formate hydrogen lyases, and on the F(0)F(1)-ATPase. In this study, it has been shown that formate markedly increased ATPase activity in membrane vesicles. This activity was significantly (1.8-fold) stimulated by 100mM K(+) and inhibited by N,N(')-dicyclohexylcarbodiimide and sodium azide. The increase in ATPase activity was absent in atp, trkA, and hyf but not in hyc mutants. ATPase activity was also markedly increased by formate when bacteria were fermenting glucose with external formate (30mM) in the growth medium. However this activity was not stimulated by K(+) and absent in atp and hyc but not in hyf mutants. The effects of formate on ATPase activity disappeared when cells were performing anaerobic (nitrate/nitrite) or aerobic respiration. These results suggest that the F(0)F(1)-ATPase activity is dependent on K(+) uptake TrkA system and hydrogenase 4, and on hydrogenase 3 when cells are fermenting glucose in the absence and presence of external formate, respectively.
在微碱性pH值的厌氧条件下以葡萄糖为生长底物的大肠杆菌进行混合酸发酵，除了其他可分泌或进一步氧化为H₂和CO₂的产物外，还会产生甲酸盐。H₂的产生很大程度上依赖于甲酸脱氢酶H以及构成两种甲酸氢化酶的氢化酶3和氢化酶4，以及F₀F₁ - ATP酶。在本研究中，已表明甲酸盐显著增加了膜囊泡中的ATP酶活性。这种活性受到100mM K⁺的显著刺激（1.8倍），并被N,N'-二环己基碳二亚胺和叠氮化钠抑制。在atp、trkA和hyf突变体中不存在ATP酶活性的增加，但在hyc突变体中存在。当细菌在生长培养基中用外部甲酸盐（30mM）发酵葡萄糖时，甲酸盐也会显著增加ATP酶活性。然而，这种活性不受K⁺刺激，在atp和hyc突变体中不存在，但在hyf突变体中存在。当细胞进行厌氧（硝酸盐/亚硝酸盐）或有氧呼吸时，甲酸盐对ATP酶活性的影响消失。这些结果表明，当细胞在不存在和存在外部甲酸盐的情况下发酵葡萄糖时，F₀F₁ - ATP酶活性分别依赖于K⁺摄取TrkA系统和氢化酶4，以及氢化酶3。
