A family of calcium-binding alpha-globulins that are synthesized in the LIVER and play an essential role in maintaining the solubility of CALCIUM in the BLOOD. In addition the fetuins contain aminoterminal cystatin domains and are classified as type 3 cystatins.

A homologous group of endogenous CYSTEINE PROTEINASE INHIBITORS. The cystatins inhibit most CYSTEINE ENDOPEPTIDASES such as PAPAIN, and other peptidases which have a sulfhydryl group at the active site.

Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)

A group of closely-related cystatins found in SALIVA.

An intracellular cystatin subtype that is found in a broad variety of cell types. It is a cytosolic enzyme inhibitor that protects the cell against the proteolytic action of lysosomal enzymes such as CATHEPSINS.

A cytastin subtype found at high levels in the SKIN and in BLOOD CELLS. Cystatin A incorporates into the cornified cell envelope of stratified squamous epithelial cells and may play a role in bacteriostatic properties of skin.

An extracellular cystatin subtype that is abundantly expressed in bodily fluids. It may play a role in the inhibition of interstitial CYSTEINE PROTEASES.

Endogenous peptides present in most body fluids. Certain enzymes convert them to active KININS which are involved in inflammation, blood clotting, complement reactions, etc. Kininogens belong to the cystatin superfamily. They are cysteine proteinase inhibitors. HIGH-MOLECULAR-WEIGHT KININOGEN; (HMWK); is split by plasma kallikrein to produce BRADYKININ. LOW-MOLECULAR-WEIGHT KININOGEN; (LMWK); is split by tissue kallikrein to produce KALLIDIN.