Generation, Characterisation and Identification of Bioactive Peptides from Mesopelagic Fish Protein Hydrolysates Using In Silico and In Vitro Approaches.

This study generated bioactive hydrolysates using the enzyme Alcalase and autolysis from mesopelagic fish, including Maurolicus muelleri and Benthosema glaciale. Generated hydrolysates were investigated for their bioactivities using in vitro bioassays, and bioactive peptides were identified using mass spectrometry in active hydrolysates with cyclooxygenase, dipeptidyl peptidase IV and antioxidant activities. In silico analysis was employed to rank identified peptide sequences in terms of overall bioactivity using programmes including Peptide Ranker, PrepAIP, Umami-MRNN and AntiDMPpred. Seven peptides predicted to have anti-inflammatory, anti-type 2 diabetes or Umami potential using in silico strategies were chemically synthesised, and their anti-inflammatory activities were confirmed using in vitro bioassays with COX-1 and COX-2 enzymes. The peptide QCPLHRPWAL inhibited COX-1 and COX-2 by 82.90% (+/-0.54) and 53.84%, respectively, and had a selectivity index greater than 10. This peptide warrants further research as a novel anti-inflammatory/pain relief peptide. Other peptides with DPP-IV inhibitory and Umami flavours were identified. These offer potential for use as functional foods or topical agents to prevent pain and inflammation.

Structure-activity relationship studies of shortened analogues of the antimicrobial peptide EeCentrocin 1 from the sea urchin Echinus esculentus.

EeCentrocin 1 is a potent antimicrobial peptide isolated from the marine sea urchin Echinus esculentus. The peptide has a hetero-dimeric structure with the antimicrobial activity confined in its largest monomer, the heavy chain (HC), encompassing 30 amino acid residues. The aim of the present study was to develop a shorter drug lead peptide using the heavy chain of EeCentrocin 1 as a starting scaffold and to perform a structure-activity relationship study with sequence modifications to optimize antimicrobial activity. The experiments consisted of 1) truncation of the heavy chain, 2) replacement of amino acids unfavourable for in vitro antimicrobial activity, and 3) an alanine scan experiment on the truncated and modified heavy chain sequence to identify essential residues for antimicrobial activity. The heavy chain of EeCentrocin 1 was truncated to less than half its initial size, retaining most of its original antimicrobial activity. The truncated and optimized lead peptide (P6) consisted of the 12 N-terminal amino acid residues from the original EeCentrocin 1 HC sequence and was modified by two amino acid replacements and a C-terminal amidation. Results from the alanine scan indicated that the generated lead peptide (P6) contained the optimal sequence for antibacterial activity, in which none of the alanine scan peptides could surpass its antimicrobial activity. The lead peptide (P6) was also superior in antifungal activity compared to the other peptides prepared and showed minimal inhibitory concentrations (MICs) in the low micromolar range. In addition, the lead peptide (P6) displayed minor haemolytic and no cytotoxic activity, making it a promising lead for further antimicrobial drug development.