Kaihovaara P, Höök-Nikanne J, Uusi-Oukari M, Kosunen T U, Salaspuro M
Research Unit of Alcohol Diseases, Institute of Biomedicine, University of Helsinki, Finland.
J Antimicrob Chemother. 1998 Feb;41(2):171-7. doi: 10.1093/jac/41.2.171.
Helicobacter pylori flavodoxin was purified to homogeneity from cell extracts of strain NCTC 11637. The molecular weight of the protein was estimated by gel electrophoresis to be 18 kDa. Oxidized flavodoxin showed an absorption spectrum with maxima at 378 nm and 453 nm, and it was reduced to a neutral form of flavin semiquinone by the electrons generated in the oxidation of pyruvate. This coenzyme A dependent pyruvate:flavodoxin oxidoreductase activity of H. pylori was also detected as a reduction of methyl viologen or cytochrome c by bacterial extracts. The apparent Km of pyruvate was 310 microM. Anaerobically incubated bacteria (10[9]) of strain NCTC 11637 produced acetate (96 +/- 16 nmol/h) from pyruvate concomitantly reducing metronidazole (17 +/- 5 nmol/h). In anaerobic conditions both sensitive and resistant H. pylori strains reduced metronidazole, and there was a significant positive correlation between acetate production and metronidazole activation (r = 0.77, P < 0.01, n = 11). In the presence of atmospheric oxygen, H. pylori excreted twice as much acetate but metronidazole was not activated. These results suggest that the pyruvate:flavodoxin oxidoreductase complex catalyses pyruvate oxidation in H. pylori. Electrons generated in this reaction are transferred to flavodoxin and under anaerobic conditions further to metronidazole (imidazoles) thus reducing the drug to its bactericidal form.
幽门螺杆菌黄素氧还蛋白从NCTC 11637菌株的细胞提取物中纯化至同质。通过凝胶电泳估计该蛋白质的分子量为18 kDa。氧化型黄素氧还蛋白显示出在378 nm和453 nm处有最大值的吸收光谱，并且通过丙酮酸氧化产生的电子将其还原为黄素半醌的中性形式。幽门螺杆菌的这种依赖辅酶A的丙酮酸：黄素氧还蛋白氧化还原酶活性也通过细菌提取物对甲基紫精或细胞色素c的还原作用检测到。丙酮酸的表观Km为310 microM。NCTC 11637菌株的厌氧培养细菌（10[9]）从丙酮酸产生乙酸盐（96±16 nmol/h），同时还原甲硝唑（17±5 nmol/h）。在厌氧条件下，敏感和耐药的幽门螺杆菌菌株均还原甲硝唑，并且乙酸盐产生与甲硝唑活化之间存在显著正相关（r = 0.77，P < 0.01，n = 11）。在大气氧存在下，幽门螺杆菌分泌的乙酸盐是原来的两倍，但甲硝唑未被活化。这些结果表明，丙酮酸：黄素氧还蛋白氧化还原酶复合物催化幽门螺杆菌中的丙酮酸氧化。该反应中产生的电子转移至黄素氧还蛋白，在厌氧条件下进一步转移至甲硝唑（咪唑类），从而将药物还原为其杀菌形式。
