Sjuts Hanno, Dunstan Mark S, Fisher Karl, Leys David
Manchester Institute of Biotechnology, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, England.
Acta Crystallogr D Biol Crystallogr. 2015 Sep;71(Pt 9):1900-8. doi: 10.1107/S1399004715013061. Epub 2015 Aug 25.
O-Demethylation by acetogenic or organohalide-respiring bacteria leads to the formation of methyltetrahydrofolate from aromatic methyl ethers. O-Demethylases, which are cobalamin-dependent, three-component enzyme systems, catalyse methyl-group transfers from aromatic methyl ethers to tetrahydrofolate via methylcobalamin intermediates. In this study, crystal structures of the tetrahydrofolate-binding methyltransferase module from a Desulfitobacterium hafniense DCB-2 O-demethylase were determined both in complex with tetrahydrofolate and the product methyltetrahydrofolate. While these structures are similar to previously determined methyltransferase structures, the position of key active-site residues is subtly altered. A strictly conserved Asn is displaced to establish a putative proton-transfer network between the substrate N5 and solvent. It is proposed that this supports the efficient catalysis of methyltetrahydrofolate formation, which is necessary for efficient O-demethylation.
产乙酸菌或有机卤化物呼吸细菌进行的O-去甲基化作用会导致从芳香族甲基醚形成甲基四氢叶酸。O-去甲基酶是一种依赖钴胺素的三组分酶系统，它通过甲基钴胺素中间体催化甲基从芳香族甲基醚转移到四氢叶酸。在本研究中，测定了来自脱硫脱硫弧菌DCB-2 O-去甲基酶的四氢叶酸结合甲基转移酶模块与四氢叶酸和产物甲基四氢叶酸形成复合物时的晶体结构。虽然这些结构与先前确定的甲基转移酶结构相似，但关键活性位点残基的位置发生了细微变化。一个严格保守的天冬酰胺发生位移，在底物N5和溶剂之间建立了一个假定的质子转移网络。有人提出，这有助于高效催化甲基四氢叶酸的形成，而这是高效O-去甲基化所必需的。
