ALBERT

Description: 〈p〉Publication date: Available online 29 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Fish & Shellfish Immunology〈/p〉 〈p〉Author(s): Sarithaa Sellaththurai, Thanthrige Thiunuwan Priyathilaka, Jehee Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Organisms possess a cellular antioxidant defense system inclusive of ROS scavengers to maintain the homeostasis of antioxidant levels. Catalase is a major ROS scavenger enzyme that plays a significant role in the antioxidant defense mechanism of organisms by reducing toxic hydrogen peroxide molecules into a nontoxic form of oxygen and water with a high turnover rate. In the present study, we performed molecular and functional characterization of the catalase homolog from 〈em〉Hippocampus abdominalis〈/em〉 (HaCat). The 〈em〉HaCat〈/em〉 cDNA sequence was identified as a 1578 bp ORF (open reading frame) that encodes a polypeptide of 526 amino acids with 59.33 kDa molecular weight. Its estimated pI value is 7.7, and it does not have any signal sequences. HaCat shared a conserved domain arrangement including the catalase proximal active site signature and heme ligand signature domain with the previously identified catalase counterparts. Phylogenetic analysis displayed close evolutionary relationships between HaCat and catalases from other teleost fish. According to our qPCR results, ubiquitous expression of 〈em〉HaCat〈/em〉 transcripts were observed in all the tested tissues with high expression in the kidney followed by liver. Significant modulations of 〈em〉HaCat〈/em〉 transcription were observed in blood, liver, and kidney tissues post-challenge with 〈em〉Streptococcus iniae〈/em〉, 〈em〉Edwardsiella tarda〈/em〉, poly I:C, and LPS. Peroxidase activity of recombinant HaCat (rHaCat) was evaluated using an ABTS assay and the ROS removal effect was further confirmed by oxidative DNA damage protection and cell viability assays. The rHaCat showed more than 97% activity over a temperature and pH range of 10 °C–40 °C and 5 to 6, respectively. The above results suggest that HaCat plays an indispensable role in the oxidative homeostasis of the seahorse during pathogenic attack.〈/p〉〈/div〉 〈/div〉