Characterization of teleost phagocyte NADPH oxidase: Molecular cloning and expression analysis of carp (Cyprinus carpio) phagocyte NADPH oxidase

We previously demonstrated that some fish have unique response in the form of reactive oxygen species (ROS) production. In the present study, we cloned and sequenced the full-length cDNAs for carp (Cyprinus carpio) phagocyte NADPH oxidase components: gp91^phox, p22^phox, p47^phox, p67^phox and p40^phox. These amino acid sequences were compared with other teleost and mammalian homologues, to elucidate the features of ROS production of fish neutrophils. The phylogeny analysis clearly demonstrates that the radiation of phagocyte oxidase components took place in the common ancestor of teleosts and mammals. Thereafter, the overall structure and expression pattern of phagocyte oxidase have been highly conserved in two different strains. However the amino acid identity of p67^phox and p47^phox was relatively lower than the amino acid identities of other components. Moreover, a synteny analysis supports the hypothesis that there was strong selective pressure in the p67^phox and p47^phox genes. Thus, it is likely that the higher divergence of p67^phox and p47^phox are responsible for the difference of ROS responses between different species of teleosts.