麦芽根中核酸酶的分离纯化及性质研究

采用硫酸铵沉淀及色谱分离技术对麦芽根中核酸酶进行了分离纯化，通过Sephacryl S-200,DEAE Sephadex A-50 and Sephacryl S-2003步色谱分离，得到了部分纯化的两种核酸酶(Ⅰ和Ⅱ)，核酸酶Ⅰ的纯化倍数为94，核酸酶Ⅱ的纯化倍数为1790.高效液相色谱显示两种酶作用于酵母RNA的产物均为5′-核苷酸.核酸酶Ⅰ的热稳定性比核酸酶Ⅱ好，在55℃下保温2h后，核酸酶I的活力损失仅13%，而核酸酶Ⅱ则高达64%.两种酶的最适温度分别为55℃和65℃.两种酶的pH稳定性相似，在pH2.5～9.0范围内很稳定.核酸酶Ⅰ的最适pH值为5.0和8.0～8.5，核酸酶Ⅱ的最适pH范围为4.0～5.5.

Separation, Purification and Properties of RNase in Malted Barley Roots

Two RNases (Ⅰ and Ⅱ) were isolated from extracts of malted barley roots by ammonium sulfate precipitation and purified by chromatography on Sephacryl S-200, DEAE SephadexA-50 and Sephacryl S-200 consecutively. The RNase Ⅰ was purified by 94 fold and RNase Ⅱ 1790 fold. Reaction products of these two RNases with yeast RNA were all 5′- nucleotides determined by HPLC. The heat stability of RNase Ⅰ was better than that of RNase Ⅱ. Activity loss was 64% for RNase Ⅱ and less than 13%　for RNase Ⅰ after 2　h at 55　℃. The optimum temperatures of RNase Ⅰ and RNase Ⅱ were 65 ℃ and 55　℃ respectively. The pH stability of these two enzymes was similar and they were stable in the pH　2.5～9.0. The optimum pHs were 5.0 and 8.0～8.5 for RNase Ⅰ, and pH　4.0～5.5 for RNase Ⅱ.