中文摘要：

研究分离纯化发酵乳杆菌细胞壁蛋白酶（cell envelope proteinase,CEP）的方法及其酶学性质。用50mmol/LTris-HCl缓冲液（pH7.8）悬浮菌体,进行超声波破碎,细胞质量浓度为0.06g/mL,破碎功率330W,工作220次（工作时间3s,间隔时间5s）,离心取上清液即为粗酶液。60%硫酸铵沉淀,Sephacryl S-300 HR凝胶层析,Native-PAGE割胶回收纯化发酵乳杆菌的CEP。用纯化的CEP酶解脱脂乳,酶解液ACE（angiotensin I-converting enzyme）抑制率为50%。SDS-PAGE检测CEP分子质量为32.5kD,最适酶反应温度为41℃,最适酶反应pH值为8.0。Mg2＋、Co2＋、Ca2＋对CEP活性有激活作用;Zn2＋、Ni2＋、PMSF、EDTA对CEP活性有抑制作用,说明CEP为丝氨酸蛋白酶且酶的活性中心结构的维持与金属离子有关。

英文摘要：

The purification process of cell envelope protease（CEP） from Lactobacillus fermentum was explored in this paper.Cells were suspended in 50 mmol/L Tris-HCl（pH 7.8） and subjected to ultrasonication（cell concentration of 0.06 g/mL,ultrasonic power of 330 W,ultrasonic treatment time of 3 s with intermission of 5 s,and repeated ultrasonic treatment number of 220）.The supernatant was collected,precipitated with 60% saturated（NH4）2SO4 solution and separated by Sephacryl S-300 HR chromatography.The active protease was recovered from Native-PAGE gel.The ACE inhibitory rate of purified CEP was 50%.The molecular mass of purified CEP estimated by SDS-PAGE was approximately 32.5 kD.Maximum activity was reached at pH 8.0 and 41℃.The activity of CEP could be activated by Mg2＋,Co2＋ and Ca2＋ and inhibited by Zn2＋,Ni2＋ and PMSF,suggesting that CEP belongs to serine protease.On the other hand,its activity could also be inhibited by EDTA,suggesting that CEP is a metallopeptidase.