FunctionThis protein strongly inhibits papain and ficin, partially inhibits stem bromelain and bovine cathepsin C, but does not inhibit porcine cathepsin B or clostripain. Papain is inhibited non-competitively.
Tissue specificityExpressed in submandibular and sublingual saliva but not in parotid saliva (at protein level). Expressed in saliva, tears, urine and seminal fluid.
Sequence similaritiesBelongs to the cystatin family.
Post-translational modificationsPhosphorylated at both its N- and C-terminal regions.