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前期分离得到1株具有较强裂解能力的大肠杆菌噬菌体vB＿EcoM?ep3。测序后发现，噬菌体vB＿EcoM?ep3的裂解酶基因在大肠杆菌噬菌体中尚未报道，能够编码一种新的裂解酶，并与绿脓杆菌噬菌体裂解酶具有很高同源性。为了探讨该裂解酶对大肠杆菌和绿脓杆菌的裂解活性，克隆了vB＿EcoM?ep3的裂解酶基因，经原核表达和纯化，体外评价了Lysep3裂解活性。结果表明：克隆裂解酶基因Lysep3长为492 bp；表达蛋白分子质量为17?7 ku；裂解酶单独作用时，对大肠杆菌和绿脓杆菌均不能裂解，但是能够显著抑制生长；与柠檬酸配合使用（0?5 mg／mL终浓度的Lysep3和0?5 mmol／L终浓度的柠檬酸），对大肠杆菌和绿脓杆菌均表现出较好的裂解能力，作用从2～24 h持续有效，细菌数量分别下降7?2倍和17?3倍。该结果表明，vB＿EcoM?ep3的裂解酶不但在基因序列上与绿脓杆菌存在进化关系，在功能上也具有相关性。该研究为解析裂解酶结构与功能的关系提供了一个良好的例证，同时有助于裂解酶的广谱性改造。“,”An E. coli phage vB_EcoM?ep3 with good lysis ability was isolated in early experiments. We found an unreported lyase gene(Lysep3)could encode a novel lyase in E. coli phage showing high homology with P. aeruginosa phage lyase after the sequence analysis. To explore lysis activity of Lysep3 in P. aeruginosa and E. coli, gene cloning, prokaryotic expression, protein purification and lysis activity determination in vitro were performed. Results showed that length of lyase gene is 492 bp and protein molecular mass is 17?7 ku. When using Lysep3 (0?5 mg/mL) alone, P. aerugi?nosa and E. coli were not lysed while growth could be significantly inhibited. When using Lysep3 and citric acid (0?5 mmol/L) in combination, better lysis ability was displayed ( with continual effect from 2 h to 24 h) ,and quantity of bacteria decreased 7?2 times and 17?3 times respectively. Results suggested that the evolutionary relationship of lyase between vB_EcoM?ep3 and P. aeruginosaare re?presented in both gene sequence and function. These results not only provide strong evidence for the study on relationship between structure and function of lysine, but also contribute to the transforma?tion of a broad spectrum lyase.