【摘要】 通过硫酸铵沉淀,低温透析,初步纯化了烤烟成熟期叶片中的蛋白酶,并对其主要性质进行了研究。结果表明:以酪蛋白为底物,其最适pH值为5.0,最适温度为50℃;酶的热稳定性随着温度的升高而迅速降低,酶的pH稳定性随着保存时间的延长先增大后降低,保存40 m in时活性最大。研究还发现低浓度的K+,Cu2+,M g2+,F e2+,A l3+,F e3+对蛋白酶有抑制作用,C a2+,Zn2+,DTT对蛋白酶有激活作用。随着DTT,巯基乙醇,C a2+浓度升高,对蛋白酶的激活作用增强。更多还原

【Abstract】 The proteinases extracted from mature leaves of flue-cured tobacco were purified by the ammonium sulfate sediment and low-temperature dialysis,and characterized.The results showed that the proteinases had the optimal pH of 5.0 and the optimal temperature of 50℃ when casein was used as a substrate.Their thermo stability decreased as the temperature rose while their pH stability increased first and decreased then as the preservation prolonged,with the activity reaching the peak at 40 min of preservation.K⁺,Cu²⁺,Mg²⁺,Fe²⁺,Al³⁺ and Fe³⁺ inhibited the activity at the low concentration whereas Ca²⁺,Zn²⁺ and DTT activated the enzyme.Effect of activation increased with rise in the concentrations of DTT,mercaptoethanol and Ca²⁺.更多还原