Lysozymes play a key role in innate immune response to bacterial pathogens, catalyzing the hydrolysis of the peptidoglycan layer of bacterial cell walls. In this study, the genes encoding the c-type (TmLyzc) and g-type (TmLyzg) lysozymes from Totoaba macdonaldi were cloned and characterized. The cDNA sequences of TmLyzg and TmLyzc were 582 and 432 bp, encoding polypeptides of 193 and 143 amino acids, respectively. Amino acid sequences of these lysozymes shared high identity (60-90%) with their counterparts of other teleosts and showed conserved functional-structural signatures of the lysozyme superfamily. Phylogenetic analysis indicated a close relationship with their vertebrate homologues but distinct evolutionary paths for each lysozyme. Expression analysis by qRT-PCR revealed that TmLyzc was expressed in stomach and pyloric caeca, while TmLyzg was highly expressed in stomach and heart. These results suggest that both lysozymes play important roles in defense of totoaba against bacterial infections or as digestive enzyme.

溶菌酶在对细菌病原体的先天免疫反应中起关键作用，催化细菌细胞壁肽聚糖层的水解。在这项研究中，编码来自Totoaba macdonaldi的 c 型 (TmLyzc) 和 g 型 (TmLyzg) 溶菌酶的基因被克隆和表征。TmLyzg和TmLyzc的cDNA序列分别为582和432 bp，分别编码193和143个氨基酸的多肽。这些溶菌酶的氨基酸序列与其他硬骨鱼类的对应物具有高度的同一性 (60-90%)，并显示出溶菌酶超家族的保守功能结构特征。系统发育分析表明与它们的脊椎动物同源物密切相关，但每种溶菌酶的进化路径不同。qRT-PCR的表达分析显示TmLyzc在胃和幽门盲囊中表达，而TmLyzg在胃和心脏中高表达。这些结果表明，这两种溶菌酶在防止石首鱼抵御细菌感染或作为消化酶方面发挥着重要作用。