MOLECULAR INSIGHTS, EXPRESSION ANALYSIS AND RADICAL SCAVENGING ACTIVITY OF NOVEL PROTEIN THIOREDOXIN DOMAIN CONTAINING PROTEIN 17 FROM Hippocampus abdominalis

Thioredoxin is an intracellular protein ubiquitously found in all kingdoms of living organisms. It possesses a redox active thiol di-sulfide CXXC motif with two cysteines. Thioredoxin protects the proteins and cellular organelles from the oxidative aggregation and inactivation, protect the cells from environmental stresses like reactive oxygen species (ROS), arsenate and peroxynitrite and apoptosis via programmed cell death. The big-belly seahorse (Hippocampus abdominalis) is an important seahorse species in oriental medicine, ability to suppress neuroinflammatory responses and collagen release. Also, it exhibits antitumor, anti-aging properties. In this study, novel thioredoxin domain-containing protein 17 (TXNDC17) from the big-belly seahorse were characterized. The open reading frame (ORF) of TXNDC17 369 bp and comprises 123 amino acids. The estimated molecular mass and the predicted isoelectric point (pI) of TXNDC17 was 14.1 kDa and 5.04 respectively. According to the pairwise alignment of amino acids with other TXNDC17 orthologs, 99.2% of highest identity was revealed with Hippocampus comes. The phylogenetic tree showed TXNDC17 were positioned within the teleost group.

Spatial expression profile of TXNDC17 under normal physiological conditions was observed in 14 different tissues. The highest mRNA expression level of TXNDC17 was detected in muscle (12.81-fold) and the lowest expression observed in spleen (Figure 1). TXNDC17 normally exhibit a broad range of tissue distribution due to the essentiality of maintaining cellular redox homeostasis. Highest TXNDC17 availability usually occurred in the organs with the high antioxidant requirement.

According to the radical scavenging assay, figure 2 shows the percentage of DPPH radical scavenging capacity of TXNDC17 with ascorbic acid as a reference compound. A concentration-dependent relationship was found in the radical scavenging activity of TXNDC17. The protein showed maximum 319.76 % inhibition of DPPH radicals within the concentration range. Further, TXNDC17 showed IC50 value at the concentration of 25.73 µg/mL. TXNDC17 from the Hippocampus abdominalis is assessing for the first time in fish by this study and provides better knowledge about the TXNDC17 gene and their functional domain insights to the fish and aquaculture industry.