中文摘要：

蚯蚓组织的NaAc抽提液经过热变性、酸变性和丙酮分段沉淀，再经过DEAE-Sepharose和CM-Sepharose层析纯化，从中分离纯化得到一种脱氧核糖核酸酶（EWD2），经SDS-PAGE电泳、基质辅助激光解吸附电离飞行时间质谱法（MALDI-TOF）、毛细管等点聚焦电泳法测定，此DNase的相对分子质量测定为69100，明显大于已发现的DNase Ⅰ和DNase Ⅱ。该酶的等电点为6．05，温度稳定性、pH稳定性、激动剂和抑制剂等各项参数，与已发现的各种DNase相比较有明显差别。结果提示，蚯蚓组织中发现的这种脱氧核糖核酸酶具有特殊的酶学性质，可能是一种新型脱氧核糖核酸酶，其作用机理和分类还有待于进一步的研究。

英文摘要：

The earthworm Eisenia foetida was extracted overnight with NaAc at 4℃, followed by heating-denature, and acid-denature for the extract supernatant. Then a two-step precipitation with freezed acetone（15% and 50%） was performed. The crude protein obtained was purified by DEAE-Sepharose, followed by CM-Sepharose filtration. The purified protein named EWD2 was obtained. The EWD2 is a monomeric protein with a relative molecular weight of 69. 1 kDa estimated by SDS-PAGE, Sephacryl S200 filtration and MALDI-TOF, which is much higher than that of DNase Ⅰ and DNase Ⅱ. The pI of EWD2, measured by Capillary Electrophoresis Isoelectric Focusing （CE-IEF）,was 6. 05. Several parameters of EWD2, for example temperature stability, pH stability, activators and inhibitors are significantly different from those of DNases which have already been found. All of these data indicate that the EWD2 derived from the earthworm has unique enzymatic characteristics, and it is a new kind of deoxyri-bonuclease possibly. Its mechanism of action and classification will be studied in future.