Cystatin C a protein encoded by the CST3 gene, with molecular weight of 13260 Da, is composed of 120 amino acids, lacks carbohydrate and has two disulfide bridges located near the carboxyl terminus. Cystatin C is mainly used as a biomarker of kidney function. If kidney function and glomerular filtration rate decline, the blood levels of cystatin C rise. Recently, it has been studied for its role in predicting new-onset or deteriorating cardiovascular disease. It also seems to play a role in brain disorders involving amyloid (a specific type of protein deposition), such as Alzheimer's disease.
Background References
1. Chen DC et al. Advantages, Limitations, and Clinical Considerations in Using Cystatin C to Estimate GFR. Kidney360. 2022 Aug
2. Skidmore M et al. Cystatin C as a Marker of Kidney Function in Children. Biomolecules. 2024 Aug
Sequence Similarity
Belongs to the cystatin family.
Tissue Specificity
Expressed in submandibular and sublingual saliva but not in parotid saliva (at protein level). Expressed in various body fluids, such as the cerebrospinal fluid and plasma. Expressed in highest levels in the epididymis, vas deferens, brain, thymus, and ovary and the lowest in the submandibular gland.
Post-translational Modification
The Thr-25 variant is O-glycosylated with a core 1 or possibly core 8 glycan. The signal peptide of the O-glycosylated Thr-25 variant is cleaved between Ala-20 and Val-21.