Host-defense peptide that maintains sterility in the urogenital system (By similarity). Has antimicrobial activity against a wide range of bacteria, including Gram-negative E.coli, P.aeruginosa and S.typhimurium, and Gram-positive E.aerogenes, S.aureus, B. cereus, E.faecium and L.monocytogenes (By similarity). Confers resistance to intestinal infection by S.typhimurium (By similarity). Exhibits antimicrobial activity against enteric commensal bacteria such as B.adolescentis, L.acidophilus, B.breve, L.fermentum, B.longum and S.thermophilus (By similarity). Binds to bacterial membranes and causes membrane disintegration (By similarity). Induces the secretion of the chemokine IL-8 by intestinal epithelial cells (By similarity). Binds to B.antracis lef/lethal factor, a major virulence factor from B.anthracis, and neutralizes its enzymatic activity (By similarity). Homodimer (By similarity). Homotetramer (By similarity). Interacts with B.antracis lef/lethal factor (By similarity). Stored as propeptide HD5(20-94) in secretory granules of small intestinal Paneth cells and found in the ileum lumen as processed mature peptides, predominantly in the HD5(63-94) form. Peptides HD5(20-94), HD5(23-94) and HD5(29-94) are found within tissues, HD5(20-94) being the predominant intracellular form. Peptides HD5(56-94) and HD5(63-94) are found in the extracellular milieu, HD5(63-94) being the most abundant form (By similarity). Secreted into the female genital tract lumen (By similarity). Glycosylated. Proteolytically cleaved at Arg-62 by trypsin (By similarity). Both the propeptide form proHD5/HD5(20-94) and HD5(56-94) are cleaved into the lumenal peptide form HD5(63-94) by trypsin (By similarity). Unprocessed proHD5 exerts antimicrobial activities, but peptide potency is enhanced by peptide processing (By similarity). Proteolytically cleaved in duodenal fluid; derived fragments are antimicrobially active against commensal bacteria (in vitro) (By similarity). Belongs to the alpha-defensin family. It was shown by two studies that dimerization of DEFA5 is crucial for antimicrobial activity (By similarity). Another study, however, states that dimer formation is not indispensable for antimicrobial activity of DEFA5 (By similarity).