Subramanian Sangeetha, MacKinnon Shawna L, Ross Neil W
National Research Council-Institute for Marine Biosciences, Nova Scotia, Canada B3H 3Z1.
Comp Biochem Physiol B Biochem Mol Biol. 2007 Nov;148(3):256-63. doi: 10.1016/j.cbpb.2007.06.003. Epub 2007 Jun 14.
Fish epidermal mucus and its components provide the first line of defense against pathogens. Little is known about the role of epidermal mucus enzymes in the innate immune system of fish species such as Arctic char (Salvelinus alpinus), brook trout (S. fontinalis), koi carp(Cyprinus carpio), striped bass (Morone saxatilis), haddock, (Melanogrammus aeglefinus), Atlantic cod (Gadus morhua) and hagfish (Myxine glutinosa). The epidermal mucus samples from these fish were analysed for the specific activities of various hydrolytic enzymes including lysozyme, alkaline phosphatase, cathepsin B and proteases and the enzyme levels were compared among the fish species. Of all the species hagfish mucus showed a high activity for lysozyme and proteases and koi carp mucus had the highest levels of alkaline phosphatase and cathepsin B. A wide variation in enzyme activities was observed among the seven species and also between species of same family such as Arctic char and brook trout (salmonidae), haddock and cod (gadidae). Only lysozyme levels showed a marked variation with salinity where seawater fish showed approximately two times higher lysozyme activity than freshwater-reared fish species. Characterization of proteases with specific inhibitors showed Arctic char, brook trout, haddock and cod having higher levels of serine over metalloproteases whereas koi carp and striped bass had higher levels of metalloproteases over serine proteases. In contrast, hagfish had almost equal proportion of both serine and metalloproteases. This study demonstrates variation in the level of hydrolytic enzymes in the epidermal mucus of fish. These results provide preliminary information for a better understanding of the role of epidermal mucus and its components in the fish innate immune system.
鱼类表皮黏液及其成分构成了抵御病原体的第一道防线。对于诸如北极红点鲑（Salvelinus alpinus）、溪红点鲑（S. fontinalis）、锦鲤（Cyprinus carpio）、条纹鲈（Morone saxatilis）、黑线鳕（Melanogrammus aeglefinus）、大西洋鳕鱼（Gadus morhua）和盲鳗（Myxine glutinosa）等鱼类物种的表皮黏液酶在其先天免疫系统中的作用，人们了解甚少。对这些鱼类的表皮黏液样本进行了分析，以测定包括溶菌酶、碱性磷酸酶、组织蛋白酶B和蛋白酶在内的各种水解酶的比活性，并在不同鱼类物种之间比较了酶水平。在所有物种中，盲鳗黏液的溶菌酶和蛋白酶活性较高，而锦鲤黏液的碱性磷酸酶和组织蛋白酶B水平最高。在这七个物种之间以及同一科的物种（如北极红点鲑和溪红点鲑（鲑科）、黑线鳕和鳕鱼（鳕科））之间都观察到酶活性存在很大差异。只有溶菌酶水平随盐度有显著变化，海水鱼的溶菌酶活性比淡水养殖的鱼类大约高两倍。用特异性抑制剂对蛋白酶进行表征显示，北极红点鲑、溪红点鲑、黑线鳕和鳕鱼的丝氨酸蛋白酶水平高于金属蛋白酶，而锦鲤和条纹鲈的金属蛋白酶水平高于丝氨酸蛋白酶。相比之下，盲鳗的丝氨酸蛋白酶和金属蛋白酶比例几乎相等。这项研究证明了鱼类表皮黏液中水解酶水平的差异。这些结果为更好地理解表皮黏液及其成分在鱼类先天免疫系统中的作用提供了初步信息。
