近年来在多种生物体中都发现有抗菌活性蛋白和多肽。由于其具有生物化学多样性，抗病毒、微生物、真菌、原生动物、肿瘤，促进伤口愈合等生物学活性，而引起研究者的极大兴趣。抗菌活性蛋白和多肽在动物的先天免疫中具有重要作用，它们直接作用于细菌，并将其杀死。鲑点石斑鱼(Epinephelus fario)是中国南方水产养殖中重要的海水鱼。近年来，由于细菌和病毒引发的病害造成鲑点石斑鱼大量死亡，但其抗菌活性蛋白及多肽目前还未见报道。本研究发现鲑点石斑鱼皮肤具有抗菌活性成分，鲑点石斑鱼皮肤匀浆物经胰蛋白酶水解后抗菌活性丧失，说明该活性是由蛋白质引起的。经离子交换层析及凝胶过滤层析，从鲑点石斑鱼皮肤中分离纯化到抗菌活性蛋白（Efap）。SDS-PAGE显示，Efap为单链蛋白，分子量约41 kD。该成分能同时抑制革兰氏阳性菌，如金黄色葡萄球菌、滕黄微球菌、枯草牙胞杆菌和革兰氏阴性菌，如溶藻弧菌、副溶血弧菌、河流弧菌、多杀性巴氏杆菌、嗜水气单胞菌、大肠杆菌和铜绿假单胞菌。革兰氏阴性菌中，溶藻弧菌、副溶血弧菌、河流弧菌和多杀性巴氏杆菌对Efap较敏感，MIC<20 mol/L，其他3种菌敏感性较差，MIC>20 mol/L。另外，Efap显示出较强的抗金黄色葡萄球菌的活性，MIC为5—10 mol/L。Efap的广谱抗菌性，说明其在鲑点石斑鱼免疫防御中具有一定的作用。
Antimicrobial proteins and peptides had been found from a wide variety of organisms in the last few years. These molecules have attracted much research interest because of their biochemical diversity, broad specificity on anti-viral, anti-bacterial, anti-fungi, anti-protozoan parasites, anti-tumoural, and wound-healing effects. Antimicrobial proteins and peptides play key roles in innate immunity. They interact directly with bacteria and kill them. The brown-spotted grouper, Epinephelus fario, is an important marine fish cultured in southern China. Recently, bacteria and virus have caused high mortality in E. fario cultures, but its endogenous antimicrobial peptides and proteins have not been explored. An antimicrobial component was found from the skin homogenate of E. fario. After the skin homogenate was digested with trypsin, its antimicrobial activity was lost, which showed that the antimicrobial component is a protein. The antimicrobial protein (Efap) was purified from the skin homogenate of E. fario by successive ion-exchange and gel filtration chromatography. Efap was demonstrated to be single protein band by SDS-PAGE, with the apparent molecular weight of 41 kD. Efap exhibited antimicrobial activity both for the Gram-positive bacteria, Staphylococcus aureus, Micrococcus luteus and Bacillus subtilis, and for the Gram-negative bacteria, Vibrio alginolyticus, Vibrio parahaemolyticus, Vibrio fluvialis, Pasteurella multocida, Aeromonas hydrophila, Eschrrichiu coli, and Pseudomonas aeruginosa. Except A. hydrophila, P. aeruginosa, and E. coli (MIC>20 mol/L), most of the tested Gram-negative bacteria were sensitive to Efap (MIC<20 mol/L). Interestingly, Efap showed potent antimicrobial activity against Gram-positive bacteria S. aureus (MIC 5-10 mol/L) but comparatively weak antimicrobial activity against M. luteus and B. subtilis. The broad antimicrobial activities of Efap suggest that it contributes to the innate host defence of E. fario.