Tvete T, Haugan K
Nord-Trondelag University College, Faculty of Education, Engineering and Nursing, Rostad, Levanger, Norway.
J Fish Dis. 2008 May;31(5):343-52. doi: 10.1111/j.1365-2761.2008.00906.x. Epub 2008 Mar 19.
Antibacterial chemicals in the mucus of fish such as lysozyme, lectins, peptides and proteases provide an efficient first line of defence against pathogens. This study shows that there are at least three antibacterial proteins in plaice skin mucus in addition to lysozyme. One of these proteins is responsible for approximately 74% of the antibacterial activity and is a 630 kDa protease complex designated KilC (bacterial killing metalloprotease C). Purified KilC kills the bacteria Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa efficiently. The protease activity of KilC is dependent upon the divalent cation Mg(2+) and shows pH dual optima of 5.0 and 8.0. The enzyme has a temperature optimum of 25 degrees C and is made up of at least five different sized peptides. Studies with protease inhibitors show that the catalytic site of KilC may be cysteine- or serine protease-like. KilC may kill bacterial cells by acting directly upon the bacteria or by producing low molecular weight bioactive compounds such as peptides.
鱼类黏液中的抗菌化学物质，如溶菌酶、凝集素、肽和蛋白酶，构成了抵御病原体的有效第一道防线。这项研究表明，除溶菌酶外，鲽鱼皮肤黏液中至少还有三种抗菌蛋白。其中一种蛋白约占抗菌活性的74%，是一种630 kDa的蛋白酶复合物，命名为KilC（细菌杀伤金属蛋白酶C）。纯化后的KilC能有效杀死金黄色葡萄球菌、大肠杆菌、枯草芽孢杆菌和铜绿假单胞菌。KilC的蛋白酶活性依赖于二价阳离子Mg(2+)，其pH值双最佳值为5.0和8.0。该酶的最适温度为25摄氏度，由至少五种不同大小的肽组成。蛋白酶抑制剂研究表明，KilC的催化位点可能类似半胱氨酸或丝氨酸蛋白酶。KilC可能通过直接作用于细菌或产生低分子量生物活性化合物（如肽）来杀死细菌细胞。
