Histatin-3, a 32 amino acid peptide, possesses powerful antimicrobial properties. Histatin-3 behaves as a substrate for proprotein convertase 1 (PC1), being cleaved by this endoprotease primarily at a site carboxy terminal to the single Arg25 residue (HRGYR decrease SN). Histatin-3 is a moderately potent, reversible and competitive inhibitor of the furin-mediated cleavage of the pentapeptide pGlu-Arg-Thr-Lys-Arg-MCA fluorogenic substrate, with an estimated inhibition constant Ki of 1.98 μM.