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.
Keywords: Innate immunity; Lysozyme superfamily; Totoaba; c-type lysozyme; g-type lysozyme.
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