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A procedure for the partial purification of a non-specific alkaline phosphatase (EC 3.1.3.1.) from the embryonic axes of chick-pea seeds is described. Ammonium sulphate precipitation, DEAE-cellulase chromatography, Sephacryl S-200 chroma-tography and polyacrylamide gel electrophoresis are the most important steps. The molecular weight of this non-specific enzyme, as determined by Sephacryl S–200 gel filtration and SDS–polyacrylamide gel electrophoresis, was estimated as being 68 and 78 kDa respectively; the optimum pH for p-nitrophenylphosphate hydrolysis was 7.5, and the Km for this artificial substrate was 0.5 mM. The enzyme catalyzes the hydrolysis of a variety of organic phosphate esters. The best substrates are: phos-phoenolpymvate (Km = 2.4 m M ), NADP+ (Km = 4.0 m M ), 5'-AMP (Km = 4.5 m M ), 5'-ADP (Km = 6.1 m M ) and ribose-5P (Km = 5.8 m M ); but it is unable to hydrolyze 5'-ATP, phosphocreatine and tripolyphosptiate. Phospate was a competitive inhibitor. Zn2+ , K+ , Hg2+ and Mo6+ were strong inhibitors, whereas F− and Ca2+ inhibited weakly; Co2+ and Ni2+ were activators. 相似文献
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