Martínez Murillo F, Gugliuzza T, Senko J, Basu P, Stolz J F
Department of Biological Sciences, Duquesne University, Pittsburgh, PA 15282, USA.
Arch Microbiol. 1999 Nov;172(5):313-20. doi: 10.1007/s002030050785.
Nitrate reduction in the dissimilatory iron-reducing bacterium Geobacter metallireducens was investigated. Nitrate reductase and nitrite reductase activities in nitrate-grown cells were detected only in the membrane fraction. The apparent K(m )values for nitrate and nitrite were determined to be 32 and 10 microM, respectively. Growth on nitrate was not inhibited by either tungstate or molybdate at concentrations of 1 mM or less, but was inhibited by both at 10 and 20 mM. Nitrate and nitrite reductase activity in the membrane fraction was not, however, affected by dialysis with 20 mM tungstate. An enzyme complex that exhibited both nitrate and nitrite reductase activity was solubilized from membrane fractions with CHAPS and was partially purified by preparative gel electrophoresis. It was found to be composed of four different polypeptides with molecular masses of 62, 52, 36, and 16 kDa. The 62-kDa polypeptide [a low-midpoint potential (-207 mV), multiheme cytochrome c] exhibited nitrite reductase activity under denaturing conditions. No molybdenum was detected in the complex by plasma-emission mass spectrometry.
对异化铁还原菌嗜金属地杆菌中的硝酸盐还原进行了研究。仅在膜部分检测到硝酸盐生长细胞中的硝酸盐还原酶和亚硝酸盐还原酶活性。硝酸盐和亚硝酸盐的表观K(m)值分别确定为32和10 microM。在浓度为1 mM或更低时，钨酸盐或钼酸盐均不抑制硝酸盐上的生长，但在10和20 mM时均受到抑制。然而，膜部分中的硝酸盐和亚硝酸盐还原酶活性不受20 mM钨酸盐透析的影响。用CHAPS从膜部分中溶解出一种同时具有硝酸盐和亚硝酸盐还原酶活性的酶复合物，并通过制备性凝胶电泳进行部分纯化。发现它由四种不同的多肽组成，分子量分别为62、52、36和16 kDa。62 kDa多肽[低中点电位（-207 mV），多血红素细胞色素c]在变性条件下表现出亚硝酸盐还原酶活性。通过等离子发射质谱法在复合物中未检测到钼。
