Nakajima T, Uchiyama H, Yagi O, Nakahara T
a National Institute for Environmental Studies , Tsukuba 305 , Japan.
b Institute of Applied Biochemistry, University of Tsukuba , Tsukuba 305 , Japan.
Biosci Biotechnol Biochem. 1992 Jan;56(5):736-40. doi: 10.1271/bbb.56.736.
A soluble methane monooxygenase (sMMO: EC 1.14.13.25) was purified from a type II obligate methanotroph, Methylocystis sp. M. Ion exchange chromatography elution separated the sMMO into three components, I, II, and III. Components II and III were purified to homogeneity and were essential for the sMMO activity. Components II and III had molecular masses of approximately 233,000 and 39,000, respectively. Component II consisted of three subunits with molecular masses of 55,000, 44,000, and 21,000, which appeared to be present in stoichiometric amounts, suggesting a (αβγ)2 configuration in the native protein. Component II contained 1-4 mol of iron and was considered to be a hydroxylase. Component III was a flavoprotein, which contained 1 mol of FAD as well as 1-2mol of iron. It catalyzed the reduction of K3Fe(CN)6 and 2,6-dichloroindophenol by NADH. Component I, which was partially purified and not essential for sMMO activity, stimulated the activity by about 11-fold. Its stimulation could be replaced by addition of Fe(2+). The molecular mass of the partially purified component I was estimated to be from 35,000 to 40,000 based on gel filtration, which suggested the presence of a new type of regulatory protein of sMMO.
从Ⅱ型专性甲烷氧化菌甲基孢囊菌属（Methylocystis sp. M）中纯化出一种可溶性甲烷单加氧酶（sMMO：EC 1.14.13.25）。离子交换色谱洗脱将sMMO分离为三个组分，即组分Ⅰ、Ⅱ和Ⅲ。组分Ⅱ和Ⅲ被纯化至均一状态，且对sMMO活性至关重要。组分Ⅱ和Ⅲ的分子量分别约为233,000和39,000。组分Ⅱ由分子量分别为55,000、44,000和21,000的三个亚基组成，这些亚基似乎以化学计量比存在，表明天然蛋白质中存在(αβγ)2结构。组分Ⅱ含有1 - 4摩尔铁，被认为是一种羟化酶。组分Ⅲ是一种黄素蛋白，含有1摩尔FAD以及1 - 2摩尔铁。它催化NADH还原铁氰化钾（K3Fe(CN)6）和2,6 - 二氯靛酚。组分Ⅰ经过部分纯化，对sMMO活性并非必需，但能将其活性提高约11倍。添加Fe(2+)可替代其刺激作用。基于凝胶过滤法，部分纯化的组分Ⅰ的分子量估计在35,000至40,000之间，这表明存在一种新型的sMMO调节蛋白。
