LEGEND MAX™ Human Cystatin C ELISA Kit with Pre-coated Plates

Cystatin C (cystatin 3, CST3) is a cysteine protease inhibitor belonging to the type 2 cystatin superfamily. Cystatin C is a secreted, non-glycosylated protein composed of 120 residues with molecular weight of 13 kD. Its structure is characterized by an alpha-helix near the N-terminus, beta sheets at the C-terminus, and two intra-molecular disulfide bonds. It is found in all tissue and bodily fluids, and it is produced by nearly all human cells including macrophages and dendritic cells. Human cystatin C shares 68% amino acid identity with both mouse and rat.

Cystatin C exists in three forms: monomer, dimer, and complex. Only the monomeric form of cystatin C is secreted extracellularly and is functionally active as a cysteine protease inhibitor. A dimeric form is produced intracellularly through domain swapping that does not possess inhibitory properties. However, cystatin C dimer can form in more extreme conditions such as elevated temperature or low pH. Dimerization is more readily accomplished with L68Q mutant of the protein, a mutation associated with hereditary cystatin C amyloid angiopathy. Cystatin C forms reversible 1:1 complexes with target proteases such as cathepsins B, H, L, and S through its N-terminal segment, inhibiting the binding of the proteases to their substrates. Decreased cystatin C/cathepsin B complex level in serum from cancer patients indicates hindered inhibitory capacity during cancer progression.

Cystatin C is freely filtered out of the bloodstream, making it a widely used biomarker of the glomerular filtration rate (GFR), an indicator of kidney function. Cystatin C production is regulated by cytokines both positively (IL-6) and negatively (IL-10, IFN-β and IFN-γ). It has also been linked to cardiovascular disease, inflammation, neurological disorders and tumor metastasis.

BioLegend’s LEGEND MAX™ Human Cystatin C ELISA Kit is a Sandwich Enzyme-Linked Immunosorbent Assay (ELISA) with a 96-well strip plate that is pre-coated with a mouse monoclonal anti-human cystatin C capture antibody. The Detection Antibody is a biotinylated mouse monoclonal anti-human cystatin C antibody. This kit is specifically designed for the accurate quantitation of human cystatin C from cell culture supernatant, serum, plasma, urine, and saliva. It is analytically validated with ready-to-use reagents.