Histatin-3, a 32-amino-acid peptide, exhibits potent antimicrobial activities and serves as a substrate for proprotein convertase 1 (PC1), where it is primarily cleaved at a site carboxy-terminal to Arg25 (HRGYR↓SN). Additionally, it acts as a moderately potent, reversible, and competitive inhibitor of furin-mediated cleavage of the pentapeptide pGlu-Arg-Thr-Lys-Arg-MCA fluorogenic substrate, with an inhibition constant (Ki) estimated at 1.98 μM [1].