(R)-Sulfolactate dehydrogenase (EC 1.1.1.337), termed ComC, is a member of an NADH/NADPH-dependent oxidoreductase family of enzymes that catalyze the interconversion of 2-hydroxyacids into their corresponding 2-oxoacids. The ComC reaction is reversible and in the biosynthetic direction causes the conversion of (R)-sulfolactate to sulfopyruvate in the production of coenzyme M (2-mercaptoethanesulfonic acid). Coenzyme M is an essential cofactor required for the production of methane by the methyl-coenzyme M reductase complex. ComC catalyzes the third step in the first established biosynthetic pathway of coenzyme M and is also involved in methanopterin biosynthesis. In this study, ComC from Methanobrevibacter millerae SM9 was cloned and expressed in Escherichia coli and biochemically characterized. Sulfopyruvate was the preferred substrate using the reduction reaction, with 31% activity seen for oxaloacetate and 0.2% seen for α-ketoglutarate. Optimal activity was observed at pH 6.5. The apparent K_M for coenzyme (NADH) was 55.1 μM, and for sulfopyruvate, it was 196 μM (for sulfopyruvate the V_max was 93.9 μmol min⁻¹ mg⁻¹ and k_cat was 62.8 s⁻¹). The critical role of ComC in two separate cofactor pathways makes this enzyme a potential means of developing methanogen-specific inhibitors for controlling ruminant methane emissions which are increasingly being recognized as contributing to climate change.

中文翻译：

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米尔曼产甲烷甲烷短杆菌SM9的（R）-乳酸乳酸脱氢酶（ComC）的表达，纯化和表征。

（R）-乳酸乳酸脱氢酶（EC 1.1.1.337），称为ComC，是NADH / NADPH依赖性氧化还原酶家族的成员，该酶催化2-羟基酸向其相应的2-氧代酸的相互转化。ComC反应是可逆的，并且在生物合成方向上会导致（R）-巯基乳酸向辅酶M（2-巯基乙磺酸）生产中的丙酮酸丙酮酸酯转化。辅酶M是通过甲基辅酶M还原酶复合物生产甲烷所需的重要辅因子。ComC催化建立的首个辅酶M生物合成途径中的第三步，并且还参与了甲烷蝶呤的生物合成。在这项研究中，克隆了来自Methanobrevibacter millerae SM9的ComC，并在其中表达大肠杆菌及其生化特性。硫酸丙酮酸是使用还原反应的优选底物，草酰乙酸的活性为31％，α-酮戊二酸的活性为0.2％。在pH 6.5下观察到最佳活性。表观ķ_中号为辅酶（NADH）为55.1  μ M，并且用于sulfopyruvate，它为196  μ M（对于sulfopyruvate的V_最大为93.9  μ摩尔分钟^-1 毫克^-1和ķ_猫为62.8小号^-1）。ComC在两个独立的辅因子途径中的关键作用使该酶成为开发用于控制反刍动物甲烷排放的产甲烷菌特异性抑制剂的潜在手段，这种抑制剂正日益被认为是导致气候变化的原因。