Parasin I is an amphipathic antimicrobial peptide derived from the N-terminus of histone H2A of the catfish Parasilurus asotus. Parasin I has a wide antimicrobial activity and is about 12-100 times more potent than magainin 2 against a wide spectrum of microorganisms, without any hemolytic activity. In response to epidermal injury the catfish secretes parasin I into the epithelial mucosal layer, suggesting that it produces parasin I from its histone H2A by a specific protease upon injury to protect against invasion by microorganisms.
