【摘要】 采用硫酸铵盐析、SephadexG-25柱脱盐、DEAE-SepharoseFast Flow离子交换层析、SephacrylS-200分子筛层析和高效液相色谱等方法,从黑曲霉菌株Aspergillus nigerSL2-111的发酵曲中提取了一种酸性蛋白酶,经SDS-PAGE验证,该酶纯化水平已达到电泳纯.该酶的表观分子量(Mr)约为47×103,最适pH值为3.0,pH稳定性范围为2.5~6.0,最适温度为50℃,温度稳定性范围为30~60℃;Cu2+、Mn2+对其有激活作用,Hg2+、Ag+对其则有轻度的抑制作用;该酶的氨基酸组成为:中极性酸性氨基酸占17.29%,极性碱性氨基酸占4.50%,极性中性氨基酸占38.50%,其它为非极性氨基酸;N端氨基酸序列为SKGSAVTTPQ,经序列同源性比对,表明该酶与其它曲霉酸性蛋白酶具有极高的同源性.图4表5参15更多还原

【Abstract】 Acid protease prouduced by Aspergillus niger was purified to elecrophoretic homogeneity by the methods of ammonium sulfate precipitation, DEAE-Sepharose Fast Flow column chromatography, Sephacryl S-200 column chromatography and high performance liquid chromatography. Its purity was checked to be about a single band by SDS-PAGE. The molecular weight (M_r) of SL2-111 acid protease was about 47×10~3, the optimum pH 3.0 and optimum temperature 50 ℃. The enzyme activity was very stable under the pH ranging between 2.5～6.0 and under temperature ranging between 30~60 ℃. Cu~2+ and Mn~2+ showed an obvious activation to the acid protease, while Hg~2+ and~ Ag~+ slightly inhibited its activity. The acidic amino acid content of the enzyme was 17.29%, alkaline amino acid 4.50% and neutral amino acid 38.50%, and others were nonpolar amino acids. The N-terminal partial sequence was SKGSAVTTPQ, which indicated a high homology with other proteases produced by Aspergillus. Fig 4, Tab 5, Ref 15更多还原