Inhibits papain and ficin (cysteine proteinases) but not trypsin (a serine proteinase). Expressed in the skin, liver, intestine, spleen, pancreas and kidney. N-glycosylated, with sialylated biantennary complex-type glycans. O-glycosylated, sialylated oligosaccharides. Bradykinin is released from kininogen by kallikrein. The N-terminus is blocked.