Sauer K, Harms U, Thauer R K
Max-Planck-Institut für terrestrische Mikrobíologic, Fachbereich Biologie der Philipps-Universität, Marburg, Germany.
Eur J Biochem. 1997 Feb 1;243(3):670-7. doi: 10.1111/j.1432-1033.1997.t01-1-00670.x.
In Methanosarcina barkeri, methanogenesis from methanol is initiated by the formation of methylcoenzyme M from methanol and coenzyme M. This methyl transfer reaction is catalyzed by two enzymes, designated MT1 and MT2. Transferase MT1 is a corrinoid protein. The purification, catalytic properties and encoding genes of MT2 (MtaA) have been described previously [Harms, U. and Thauer, R.K. (1996) Eur. J. Biochem. 235, 653-659]. We report here on the corresponding analysis of MT1. The corrinoid protein MT1 was purified to apparent homogeneity and showed a specific activity of 750 mumol min-1 mg-1. The enzyme catalyzed the methylation of its bound corrinoid in the cob(I)amide oxidation state by methanol. In addition to this automethylation, the purified enzyme was found to catalyze the methylation of free cob(I)alamin to methylcob(III)alamin. It was composed of two different subunits designated MtaB and MtaC, with apparent molecular masses of 49 kDa and 24 kDa, respectively. The subunit MtaC was shown to harbour the corrinoid prosthetic group. The genes mtaB and mtaC were cloned and sequenced. They were found to be juxtapositioned and to form a transcription unit mtaCB. The corrinoid-harbouring subunit MtaC exhibits 35% sequence similarity to the cobalamin-binding domain of methionine synthase from Escherichia coli.
在巴氏甲烷八叠球菌中，甲醇生成甲烷的过程是由甲醇和辅酶M形成甲基辅酶M启动的。这种甲基转移反应由两种酶催化，分别命名为MT1和MT2。转移酶MT1是一种类咕啉蛋白。MT2（MtaA）的纯化、催化特性及编码基因已在之前描述过[哈姆斯，U.和绍尔，R.K.（1996年）《欧洲生物化学杂志》235卷，653 - 659页]。我们在此报告对MT1的相应分析。类咕啉蛋白MT1被纯化至表观均一，比活性为750 μmol min⁻¹ mg⁻¹。该酶催化处于钴胺酰胺氧化态的结合类咕啉被甲醇甲基化。除了这种自身甲基化外，还发现纯化后的酶能催化游离钴胺酰胺被甲基化生成甲基钴胺酰胺。它由两个不同的亚基组成，分别命名为MtaB和MtaC，表观分子量分别为49 kDa和24 kDa。亚基MtaC被证明含有类咕啉辅基。mtaB和mtaC基因被克隆并测序。发现它们相邻排列并形成一个转录单元mtaCB。含有类咕啉的亚基MtaC与大肠杆菌甲硫氨酸合酶的钴胺素结合结构域有35%的序列相似性。
