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Tuesday 24 July 2018



Definition: The cystatins are a family of cysteine protease inhibitors which share a sequence homology and a common tertiary structure of an alpha helix lying on top of an anti-parallel beta sheet. The family is subdivided as described below.

Cystatins show similarity to fetuins, kininogens, histidine-rich glycoproteins and cystatin-related proteins.

Cystatins mainly inhibit peptidase enzymes (another term for proteases) belonging to peptidase families C1 (papain family) and C13 (legumain family). They are known to mis-fold to form amyloid deposits and are implicated in several diseases.


CST1, CST2, CST3 (cystatin C, a marker of kidney function), CST4, CST5, CST6, CST7, CST8, CST9, CST11, CSTA (cystatin A), CSTB (cystatin B)[citation needed]


- cystatin C-associated amyloidosis