Abstract:
Antioxidative defense renders a significant protection against environmental stress in organisms and
maintains the correct redox balance in cells, thereby supporting proper immune function. Catalase is an
indispensable antioxidant in organisms that detoxifies hydrogen peroxides produced in cellular environments. In this study, we sought to molecularly characterize a homolog of catalase (RfCat), identified
from black rockfish (Sebastes schlegelii). RfCat consists of a 1581 bp coding region for a protein of 527
amino acids, with a predicted molecular weight of 60 kD. The protein sequence of RfCat harbored similar
domain architecture to known catalases, containing a proximal active site signature and proximal heme
ligand signature, and further sharing prominent homology with its teleostan counterparts. As affirmed
by multiple sequence alignments, most of the functionally important residues were well conserved in
RfCat. Furthermore, our phylogenetic analysis indicates its common vertebrate ancestral origin and a
close evolutionary relationship with teleostan catalases. Recombinantly expressed RfCat demonstrated
prominent peroxidase activity that varied with different substrate and protein concentrations, and
protected against DNA damage. RfCat mRNA was ubiquitously expressed among different tissues
examined, as detected by qPCR. In addition, RfCat mRNA expression was modulated in response to
pathogenic stress elicited by Streptococcus iniae and poly I:C in blood and spleen tissues. Collectively, our
findings indicate that RfCat may play an indispensable role in host response to oxidative stress and
maintain a correct redox balance after a pathogen invasion.
