甲基-辅酶M还原酶结构、功能及催化机制研究进展

Advances of structure, function, and catalytic mechanism of methyl-coenzyme M reductase

摘要:

产甲烷古菌是目前发现唯一能产生甲烷气体的微生物，也是自然界中生物甲烷的主要贡献者。甲基-辅酶M还原酶 (Methyl-coenzyme M reductase，Mcr) 负责产甲烷代谢中最后一步甲烷的生成与甲烷氧化代谢中第一步甲烷的激活反应。该酶的基因高度保守，被广泛应用于古菌的鉴定与系统发育研究。其特殊的辅因子F430及催化碳氢 (C-H) 键裂解的酶学机制也一直备受关注。近年来，在高分辨率蛋白结构和反应过渡态结构方面的重要突破有效地推动了Mcr结构与功能的研究。特别是最新发现的激活非甲烷烷烃厌氧降解的类甲基-辅酶M还原酶 (Mcr-like)，引起了众多研究者对该类酶激活惰性烷烃分子机制的浓厚兴趣。因此，文中概述了Mcr结构、功能及催化机制的最新研究进展，包括新发现的Mcr-like的研究情况，并展望了Mcr/Mcr-like酶在烷烃厌氧氧化及温室气体控制方面的未来研究方向。

关键词:产甲烷古菌，甲基-辅酶M还原酶，烷烃厌氧氧化，蛋白结构，催化机制

Abstract:

Methanogens are unique microorganisms for methane production and the main contributor of the biogenic methane in atmosphere. Methyl-coenzyme M reductase (Mcr) catalyzes the last step of methane production in methanogenesis and the first step of methane activation in anaerobic oxidation of methane. The genes encoding this enzyme are highly conserved and are widely used as a marker in the identification and phylogenetic study of archaea. There has been a longstanding interest in its unique cofactor F430 and the underpinning mechanisms of enzymatic cleavage of alkane C-H bond. The recent breakthroughs of high-resolution protein and catalytic-transition-state structures further advanced the structure-function study of Mcr. In particular, the recent discovery of methyl-coenzyme M reductase-like (Mcr-like) enzymes that activates the anaerobic degradation of non-methane alkanes has attracted much interest in the molecular mechanisms of C-H activation without oxygen. This review summarized the advances on function-structure-mechanism study of Mcr/Mcr-like enzymes. Additionally, future directions in anaerobic oxidation of alkanes and greenhouse-gas control using Mcr/Mcr-like enzymes were proposed.

Key words:methanogens, methyl-coenzyme M reductase, anaerobic oxidation of alkanes, protein structure, catalytic mechanism