Sequence analysis, characterization and tissue distribution of channel catfish (Ictalurus punctatus Rafinesque, 1818) myeloperoxidase cDNA.

Myeloperoxidase (EC 1.11.1.7), a heme-containing lysosomal glycoprotein, is found predominantly in azurophilic granules of neutrophils. This enzyme upon activation catalyzes hydrogen peroxide in the presence of various halide ions to form hypohalous acids. Subsequently, these reagents are able to kill the invading microorganisms. In this study, we report the identification, characterization and expression analysis of the channel catfish myeloperoxidase transcript. The full-length nucleotide sequence of channel catfish myeloperoxidase cDNA had 3157 nucleotides, including an open reading frame, which appears to encode a putative peptide of 771 amino acid residues with a calculated molecular mass of 87.14 kDa. By comparison with the human counterpart, the channel catfish myeloperoxidase peptide can be divided into domains and has conservative features, including peroxidase catalytic sites, covalent linkage sites for the heme group and all cysteine residues. The channel catfish myeloperoxidase transcript was detected by RT-PCR in anterior kidneys, where the major leukocyte population is neutrophil precursors. Reagent development and the role of this enzyme in Edwardsiella ictaluri infection are under investigation.