Whitman W B, Wolfe R S
J Bacteriol. 1987 Jan;169(1):87-92. doi: 10.1128/jb.169.1.87-92.1987.
Corrins inhibited the ATP-dependent activation of the methylreductase system and the methyl coenzyme M-dependent reduction of CO2 in extracts of Methanobacterium bryantii resolved from low-molecular-weight factors. The concentrations of cobinamides and cobamides required for one-half of maximal inhibition of the ATP-dependent activation were between 1 and 5 microM. Cobinamides were more inhibitory at lower concentrations than cobamides. Deoxyadenosylcobalamin was not inhibitory at concentrations up to 25 microM. The inhibition of CO2 reduction was competitive with respect to CO2. The concentration of methylcobalamin required for one-half of maximal inhibition was 5 microM. Other cobamides inhibited at similar concentrations, but diaquacobinamide inhibited at lower concentrations. With respect to their affinities and specificities for corrins, inhibition of both the ATP-dependent activation and CO2 reduction closely resembled the corrin-dependent activation of the methylreductase described in similar extracts (W. B. Whitman and R. S. Wolfe, J. Bacteriol. 164:165-172, 1985). However, whether the multiple effects of corrins are due to action at a single site is unknown.
咕啉抑制了从低分子量因子中分离出的布氏甲烷杆菌提取物中甲基还原酶系统依赖ATP的激活以及甲基辅酶M依赖的CO₂还原。对ATP依赖激活的最大抑制作用的一半所需的钴胺酰胺和钴胺的浓度在1至5微摩尔之间。在较低浓度下，钴胺酰胺比钴胺更具抑制作用。脱氧腺苷钴胺在浓度高达25微摩尔时没有抑制作用。CO₂还原的抑制作用对CO₂具有竞争性。最大抑制作用的一半所需的甲基钴胺素浓度为5微摩尔。其他钴胺在相似浓度下具有抑制作用，但二水钴胺酰胺在较低浓度下具有抑制作用。就它们对咕啉的亲和力和特异性而言，对ATP依赖激活和CO₂还原的抑制作用与类似提取物中描述的甲基还原酶的咕啉依赖激活非常相似（W. B. 惠特曼和R. S. 沃尔夫，《细菌学杂志》164:165 - 172，1985年）。然而，尚不清楚咕啉的多种作用是否是由于作用于单个位点。
