Characterization of Four Liver-Expressed Antimicrobial Peptides from Antarctic Fish and Their Antibacterial Activity

Abstract

Liver-expressed antimicrobial peptides (LEAPs) are cysteine-containing cationic peptides. LEAP-1 and LEAP-2 are eight- and four-cysteine containing antimicrobial peptides found in animals, respectively. LEAP-1 is widely known as antibacterial peptide involved in the innate immunity of fish, but the roles of LEAP-1 and LEAP-2 in Antarctic fish species are unknown. In the present study, we synthesized and characterized novel LEAPs with four and eight cysteine residues, derived from Antarctic notothenioid (Dissostichus mawsoni) and Antarctic eelpout (Lycodichthys dearborni). Circular dichroism spectroscopy of these peptides showed a typical β-sheet conformation. The LEAPs were found to be bactericidal against gram-positive as well as gram-negative bacteria. In the SYTOX green uptake assay, LEAPs did not trigger any significant increase in fluorescence. However, LEAPs competitively bound to DNA and replaced the ethidium bromide (EB) dye. To determine the effect of temperature on the activity of LEAPs, we evaluated the antibacterial activity against Listeria monocytogenes at 5, 15, 25, and 35 °C. The results showed that the antibacterial activity of LEAPs increased with a decrease in temperature, which may indicate that the Antarctic fish LEAP are evolutionarily adapted. Taken together, our results suggest that novel Antarctic LEAPs are bactericidal peptides with the likely mode of action being DNA binding and may be evolved to adapt to cold temperature.

Current Trends of Bioactive Peptides—New Sources and Therapeutic Effect

“…It has been proved that seafood proteins exhibit various bioactivities including antioxidant [ 150 , 151 , 152 , 153 , 154 , 155 , 156 ], neuroprotective [ 157 ], antidiabetic [ 158 ], ACE inhibitory [ 159 , 160 , 161 ], DPP-IV inhibitory [ 162 ], immunomodulatory [ 163 , 164 ], antibacterial [ 165 , 166 , 167 , 168 , 169 , 170 ], cholecystokinin release regulating [ 171 ], antiproliferative [ 172 , 173 ], and anticancer activities [ 155 , 174 ]. ACE inhibitory and antioxidant peptides are two the most frequent types of peptides obtained from various seafood by-products.…”

“…Antimicrobial peptides are chains of amino acids mostly with molecular weight below 10 kDa and containing less than 50 amino acids [ 184 ]. Most antimicrobial peptides from seafood have antibacterial activities against both Gram-negative and Gram-positive strains [ 167 ] due to their content of pardaxin, misgurin, cathelicidins, defensins, hepcidin, NK-lysin, piscidin, and trematocine with highly promising activities [ 168 , 169 , 170 ]. Potentially, these antimicrobial peptides are new candidates for the development of antibiotics in the pharmaceutical industry as well as antimicrobial agents for food production.…”

Identification of antibacterial activity of LEAP2 from Antarctic icefish Chionodraco hamatus

“…The search for antimicrobial peptides to target bacterial diseases in Antarctic fish is therefore urgent. Liver‐expressed antimicrobial peptide 1 (Hepcidin) has evolved in Antarctic fish as a subtype containing four cysteines (Xu et al, 2008), relative to LEAP1 containing eight cysteines, which has increased antimicrobial activity (Borkar et al, 2019; Liu et al, 2022). Liver‐expressed antimicrobial peptide 2 is the second antimicrobial peptide, containing four cysteines, whose antimicrobial activity has not been investigated in Antarctic fish.…”

Marine Transcriptomics Analysis for the Identification of New Antimicrobial Peptides

“…LEAP-2 is an important immune factor involved in the immune response against pathogens in fish [ 11 , 12 , 13 ]. LEAP-1 and -2 derived from Antarctic notothenioid ( Dissostichus mawson) and eelpout ( Lycodichthys Dearborni) revealed bactericidal activity against Gram-positive as well as Gram-negative bacteria, particularly at low temperatures [ 14 ]. Defensins have a conserved compact structure displaying a set of cationic loops and they have multiple innate immune functions [ 15 ].…”