Intestinal defense peptide (PubMed:23380721, PubMed:28345637). Has potent antibacterial activity against Gram-negative bacteria E.coli O157:H7, S.typhimurium DT104, and K.pneumoniae; and against Gram-positive bacteria S.aureus, methicillin-resistant S.aureus and L.monocytogenes (PubMed:23380721, PubMed:28345637). Remains active in the presence of NaCl and Mg(2+) (PubMed:23380721). Probably functions by disrupting bacterial membrane integrity (PubMed:28345637). However, does not show cytotoxic activity towards human intestinal cells (PubMed:23380721). Antiparallel homodimer; disulfide-linked. Specifically expressed in small intestine (jejunum and ileum) (PubMed:15494476, PubMed:23380721). Probably expressed by Paneth cells at the base of intestinal crypts (PubMed:23380721). Coexpressed with MMP7 in small intestine (PubMed:23380721). Belongs to the alpha-defensin family.