Structure, function, and therapeutic potential of defensins from marine animals

Defensins are a type of host defense peptides (HDPs), belonging to a family of cationic antimicrobial peptides (AMPs) that exhibit activity against various infectious microorganisms including bacteria, viruses, and fungi. Due to the uniqueness of the ocean's ecological environment, defensins from marine animals have a rich biodiversity and some special molecular features so as to possess significant potential. They exert antibacterial activity by binding to cell membranes, forming specific channels, or interacting with lipid II. These peptides can be utilized through various nanotechnologies, such as antimicrobial peptide-antibiotic conjugates, nanonets, and nanoparticle-based drug delivery systems, to enhance their antibacterial activities and broaden their spectra. This review summarizes the structural characteristics and classification of defensins from marine animals (mainly fish and shellfish), outlines their evolutionary trajectory, and discusses their antibacterial, antiviral, immune-regulation, and reproductive functions. Finally, the future therapeutic potential of defensins from marine animals is highlighted for fighting antibiotic resistance and treating other diseases. This review provides new insights into the future development of marine resources and natural peptides.