Characterization of the turbot Scophthalmus maximus (L.) myeloperoxidase. An insight into the evolution of vertebrate peroxidases

• Published in: Developmental & Comparative Immunology
• Main Authors: Noia Guldrís, Manuel, Fontenla Iglesias, Francisco, Valle Cao, Alejandra, Blanco Abad, Verónica, Leiro Vidal, José Manuel, Lamas Fernández, Jesús
• Other Authors: Universidade de Santiago de Compostela. Departamento de Bioloxía Funcional, Universidade de Santiago de Compostela. Departamento de Microbioloxía e Parasitoloxía, Universidade de Santiago de Compostela. Instituto de Acuicultura, Universidade de Santiago de Compostela. Instituto de Investigación e Análises Alimentarias
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier
• Subjects: Fish; Turbot; Myeloperoxidase; Eosinophil peroxidase; Scophthalmus maximus
• Online Access: http://hdl.handle.net/10347/24375; https://doi.org/10.1016/j.dci.2021.103993

We have completed the characterization of the turbot (Scophthalmus maximus) myeloperoxidase (mpx) gene and protein, which we partially described in a previous study. The turbot mpx gene has 15 exons that encode a protein of 767 aa, with a signal peptide, propeptide and light and heavy chains, and also with haem cavities, a Ca+2-binding motif and several N- and O-glycosylation sites. The mature protein forms homodimers of about 150 kDa and is very abundant in turbot neutrophils. In addition to the mpx (epx2a) gene, another three peroxidase genes, named epx1, epx2b1 and epx2b2, were identified in the turbot genome. Epx1, Epx2b1 and Epx2b2 proteins also have signal peptides and many structural characteristics of mammalian MPO and eosinophil peroxidase (EPX). Mpx was strongly expressed in head kidney, while epx2b1 and epx2b2 were strongly expressed in the gills, and epx1 was not expressed in any of the tissues or organs analysed. In vitro stimulation of head kidney leucocytes with the parasite Philasterides dicentrarchi caused a decrease in mpx expression and an increase in epx2b1 expression over time. In turbot infected experimentally with P. dicentrarchi a significant increase in mpx expression in the head kidney was observed on day 7 postinfection, while the other genes were not regulated. However, mpx, epx2b1 and epx2b2 were downregulated in the gills of infected fish, and epx1 expression was not affected. These results suggest that the four genes responded differently to the same stimuli. Interestingly, BLAST analysis revealed that Epx1 and Mpx showed greater similarity to mammalian EPX than to MPO. Considering the phylogenetic and synteny data obtained, we concluded that the epx/mpx genes of Gnathostomes can be divided into three main clades: EPX1, which contains turbot epx1, EPX2, which contains turbot mpx (epx2a) and epx2b1 and epx2b2 genes, and a clade containing mammalian EPX and MPO (EPX/MPO). EPX/MPO and EPX2 clades share a common ancestor with the chondrichthyan elephant shark (Callorhinchus milii) and ...