中文摘要：

目的：从蚯蚓组织中纯化得到一种脱氧核糖核酸酶（取名为蚯蚓脱氧核糖核酸酶,简称EDNase）并研究其酶学性质。方法：采用丙酮沉淀、离子交换层析、高效液相层析、SDS-PAGE电泳,毛细管等点聚焦电泳和基质辅助激光解吸电离飞行时间质谱等方法。结果：经证实这种纯化方案的纯化倍数是137,酶得率为45.6%。EDNase的相对分子质量约为63000。Mg^2＋,Mn^2＋和Ca^2＋对酶活性有较强的抑制作用,而Na＋则轻微的提高酶的活性。在pH4.4～5.2的范围内EDNase酶活性稳定,其最适pH值为4.8。该酶的最适温度为37℃,在40℃范围内酶具有较高的稳定性。EDNase的等电点为6.20。在以小牛胸腺DNA为底物的条件下,酶的Km为1.52g/L,Vmax为4.89mg/（mL·min）。该酶可有效降解超螺旋质粒DNA,线状λ-噬菌体DNA和细菌染色体DNA,对RNA未见任何降解作用。结论：这种酶具有独特的酶学性质,不同于以往所知的脱氧核糖核酸酶。

英文摘要：

Objective：To purify a kind of deoxyribonuclease from earthworm Eisenia foetida （named earthworm DNase, EDNase ） and study its characteristics. Methods： Acetone precipitation, ion-exchange chromatography, high performance liquid chromatography, SDS-PAGE, Capillary electrophoresis isoelectric focusing and MALDI-TOP MS were used for the study. Results： This purified protocol improved 137-fold purification and 45.6% recovery of enzyme activity. The molecular mass of EDNase was estimated to be 63 000. Mg^2＋ , Mn^2＋ and Ca^2＋ were strong inhibitors of EDNase, while Na^＋ slightly increasd the enzyme activity. The enzyme was completely stable in the pH range from 4.4 to 5.2 and had a pH optimum of 4.8. The optimum temperature was 37℃ and the enzyme was stable up to 40℃. The pI of the enzyme was 6.20.Km and Vmax for the enzyme were 1.52g/L and 4.89 mg/（mL·min）, respectively, with calf thymus DNA as substrate. The enzyme was able to degrade chromosomal DNA, linear λ-bacteriophage DNA as well as supercoiled plasmid DNA, but didn＇ t display any RNase activity. Conclusion： This kind of deoxyribonuclease possesses unique characteristics, which is different from the deoxyribonucleases which we have known before.