Characterization of Novel Antimicrobial Peptides from the Epidermis of Clarias batrachus Catfish

In this study, an antimicrobial protein (AMP) from the epidermis of catfish (Clarias batrachus) was purified and characterized for its molecular and antimicrobial properties. The crude epidermal extract was subjected to precipitation of proteins using 70% ammonium sulphate saturation followed by dialysis and protein separation by reverse phase ultra fast liquid chromotography (UFLC) using the C₁₈ column. The active peptides obtained from fractions 1, 2, and 3 were screened for antimicrobial activity against different bacterial pathogens with a minimum 5 mg/ml inhibitory concentration. An active fraction with a retention time (RT) of 27.069 from the UFLC chromatogram exhibited significant antimicrobial activity against broad-spectrum bacterial and fungal organisms, including multidrug-resistant clinical isolates. The RT 27.069, identified as cationic AMP of fraction-3, has a molecular weight of 25 kDa as determined by MALDI-TOF mass spectrometry. Further studies by Mascot search and BLAST analysis using the partial sequence of AMP showed that the protein has high homologs to pleurocidin-like peptide (Plp) from a fish Pleuronectus americanus. Moreover, the identified AMP is a cationic peptide with a good stability index, having a score of 31.50 predicted by the ProtParam. Therefore, the identified antimicrobial peptide (Plp) indicates that this cost-effective natural substance obtained from fish could potentially be used as a treatment for several bacterial and fungal infections in humans.