Inhibits hemorrhagic and proteolytic activities of metalloproteinases (HR1A, HR1B, HR2a, HR2b and H2 proteinase from T.flavodidis and brevilysins H3, H4, H6 and L4 from A.halys brevicaudus). Has no effect on brevilysins H2. Has no effect on papain and cathepsin-B. Expressed by the liver. Cys-63 may exist in a mixed disulfide form with a thiol compound such as glutathione. Is highly stable to extreme pH and heating, stability that may be conferred by the disulfide bond between Cys-28 and Cys-332. Belongs to the fetuin family.