棕色固氮菌固氮酶钼铁蛋白的几种化学修饰方法

用对氯汞苯甲酸或二巯基双二硝基苯甲酸修饰巯基。用三硝基苯磺酸、重氮四唑和焦碳酸二乙酯分别修饰氨基、酚式羟基和眯唑基。在一定范围内,被修饰钼铁蛋白在特征波长吸收值的上升和重组活性的下降与修饰剂用量的增加和时间的延长相一致,超过该范围后则光吸收和活性都保持不变。由于无氧凝胶过滤去除多余的修饰剂时未加连二亚硫酸钠,甚至正常钼铁蛋白的重组活性下降了24.2％,修饰后的铝铁蛋白活性下降范围为23.4～41.4％不等。

SEVERAL METHODS OF CHEMICAL MODIFICATION OF NITROGENASE MoFe PROTEIN FROM Azotobacter vinelandii

Sulfhydryl group is modified either by P-chloromercuric benzoate or by dithiobis (2-nitrobenzoic acid). Amino group, phenolic hydroxyl group and imidazol group are modified by trinitrobenzene sulphonic acid, diazo-1-H-tetrazole and diethyl pyrocarbonate respectively. In certain range, the increase of light absorbance at specific wave length as well as the decrease of recombination activity of modified Mo-Fe protein are in accord with the enhancement of modification reagent amount used and the prolongation of modification duration, yet beyond that range, the absorbance and activity remain unchanged. Owing to the insufficiency of sodium dithionite in the anaerobic process of gel filtration for removing excessive reagent, even the activity of normal MoFe protein for recombination is lowered by 24.2%; as for the modified protein the range of decrease of recombination activity varies from 23.4% to 41.4%.