嗜碱芽孢杆菌N6-27碱性纤维素酶的纯化及性质

The alkaline cellulase produced by alkalophilic Bacillus sp. N6-27 was purified to electrophoresis homogeneity by (NH4)2SO4 fractionation, Sepharose CL-4B hydrophobic interaction chromatography, Bio-gel P-150 chromatography. The molecular weight and pI determined by SDS-PAGE and by PAGE-IEF were 94000 and 4.2,respectively. The optimum temperature and PH for the enzymatic catalysis were 55℃ and 8.5, respectively. The enzyme activity was stable under 50℃ and in the PH range of 6-11. The substrate was carboxymethylcellulose (CMC). The enzyme activity was strongly inhibited by Fe2 +, Cu2+ and Hg2+.

牛脑皮层G_i的纯化及其与AC的偶联

用1％胆酸钠和20％饱和度的硫酸铵抽提牛脑皮层细胞膜得到含G蛋白和腺苷酸环化酶（AC）的制剂，通过Sepharose6B柱将两者分开，再将含G蛋白的级分用庚胺-Sepharose4B疏水柱、羟基磷灰石柱将其它亚型的G蛋白（主要是Gs和Go）从抑制型G蛋白（Gi）中除去，获得纯化的高活力的Gi，其GTP结合活力为17．6nmol／mg，比细胞膜Gi活力提高50倍；并具有较高的产率，从1g膜蛋白中可获得0．66mg的Gi，同时可获得无G蛋白污染的AC和少量的Gs蛋白．SDS-PAGE显示分子量为41000和36000的两条蛋白带，证实是Gi的α基和β亚基．进一步用重建脂酶体的方法检测Gi对AC的抑制作用，结果显示Gi对AC活力的抑制达40％左右，表明CAMP信息跨膜转导通路中Gi与AC之间具有较好偶联功能．