Description
Cystatin C or cystatin 3(formerly gamma trace, post-gamma-globulin or neuroendocrine basic polypeptide), a protein encoded by the CST3 gene, was originally described as a constituent of normal cerebrospinal fluid(CSF) and of urine from patients with renal failure. 1 Cystatin 3 has a low molecular weight(approximately 13. 3 kilodaltons), and it is removed from the bloodstream by glomerular filtration in the kidneys. In humans, all cells with a nucleus(cell core containing the DNA) produce cystatin C as a chain of 120 amino acids. It is found in virtually all tissues and bodily fluids. Cystatin C, which belongs to the type II cystatin gene family, is a potent inhibitor of lysosomal proteinases2(enzymes from a special subunit of the cell that break down proteins) and probably one of the most important extracellular inhibitors of cysteine proteases3(it prevents the breakdown of proteins outside the cell by a specific type of protein degrading enzymes). Moreover, cystatin C is involved in network reorganization in the epileptic dentate gyrus. 4