Therapeutic Cationic Antimicrobial Peptide (CAP) Derived from Fish Aspartic Proteinase Cathepsin D and its Antimicrobial Mechanism

Abstract

Aquatic organisms are rich in antimicrobial peptides which play key role against pathogens during infections. Cathepsin is one of immune proteases which have been proven with multiple functions including antimicrobial activity, but their role as antimicrobial peptides has not been elucidated so far in aquatic organisms. This study reports the identification and characterization of antimicrobial peptides from fish cathepsin D. Channa striatus (Cs) cathepsin D (Cath D) was identified from its established cDNA library. Multiple sequence alignment was performed to analyze the homology of CsCathD with other cathepsin. Based on the amino acid propensity scale, two putative antimicrobial regions were identified, synthesized and analyzed for their antimicrobial potency. Gene expression of CsCath D and its mRNA pattern upon pathogenic infection was also observed using real time PCR. All the bioinformatics analysis indicated the gene specific characteristic features of CsCath D. CsCathD mRNA expression was highly expressed at 24 h for bacteria (Aeromonas hydrophila) and 48 h for fungus (Aphanomyces invadans). The CsCath D derived CAPs namely, PL12 and NM12 showed their commendable inhibition towards Bacillus mycoides of the tested bacteria. The cell membrane disruption was observed with PL12 against B. mycoides in flow cytometer. With all proceedings, it is possible to conclude that CsCathD might be a potent immuno modulator and the reported CAPs could be developed as therapeutic agents to treat bacterial pathogenic infections.