CST1
Description
The CST1 (cystatin SN) is a protein-coding gene located on chromosome 20.
Cystatin-SN is a protein encoded by the CST1 gene in humans. It belongs to the cystatin superfamily, which comprises proteins with multiple cystatin-like sequences. Some members act as active cysteine protease inhibitors, while others may have lost or never acquired this inhibitory activity. The cystatin superfamily includes three inhibitory families: type 1 cystatins (stefins), type 2 cystatins, and kininogens. Type 2 cystatins, like Cystatin-SN, are cysteine proteinase inhibitors found in various human fluids and secretions, providing protective functions. The cystatin locus on chromosome 20 contains most type 2 cystatin genes and pseudogenes. CST1 is located within this locus and encodes a cysteine proteinase inhibitor present in saliva, tears, urine, and seminal fluid.
Human saliva contains multiple cysteine proteinase inhibitors related to cystatin S, differing in specificity due to amino acid sequence variations. Cystatin SN, with an isoelectric point (pI) of 7.5, demonstrates a superior inhibitory effect against papain and dipeptidyl peptidase I compared to cystatin S. Both cystatins, however, exhibit equal inhibitory potency against ficin.
CST1 is also known as -.
