商品果胶酶中endo－PG的分离纯化及其部分性质研究

Purification and Partial Characterisation of Endo-polygalacturonases from Commercial Pectinase of Aspergillus niger

以Ａ．ｎｉｇｅｒ来源的果胶酶为材料，经过ＣＭ－ＳｅｐｈａｄｅｘＣ－５０及ＳｅｐｈａｄｅｘＧ－１００两步骤分离纯化得到电泳均一的ｅｎｄｏ－ＰＧ１及ｅｎｄｏ－ＰＧ２，其亚基分子量分别为３５ｋＤ及３７ｋＤ，含糖量为１１．２２％及８．３％，最大紫外吸收峰分别在２７４ｎｍ及２６９ｎｍ处，氨基酸组成分析结果表明Ｇｌｙ含量较高，Ｍｅｔ含量较低，不含Ｃｙｓ，并且酸性氨基酸含量高于碱性氨基酸，圆二色谱结果表明二级结构主要为α螺旋和β折叠，其中ｅｎｄｏ－ＰＧ１含α螺旋４５．１％，β折叠２４．９％；ｅｎｄｏ－ＰＧ２含α螺旋３９．６％，β折叠３６．５％。

Endo-polygalacturonase (endo-PG1 and endo-PG2) was purified from a commercial preparation of Aspergillus niger pectinase by means of CM-Sephadex C-50 and Sephadex G-100 chromatography. These enzymes were electrophoretically homogeneous and the molecular weights of the subunits were 35kD (endo-PG1)and 37kD (endo-PG2). The two endo-PG displayed UV spectra with a maximam at 274nm and 269nm. Analysis showed that endo-PG had the following total sugar contents (W/W) : 11.22% (endo-PG1) and 8. 3% (endo-PG2) . The amino acid compositions of the two endo-PG were very similar:the Gly content was the highest and Met was lower,there was no Cys,acidic amino acid content was higher than basic amino acid. The CD spectra showed that endo-PG1 contained about 45. 1% α-helix,24. 9% β-pleated sheet, and endo-PG2 contained about 39. 6% α-helix, 36. 5% β-pleated sheet.