CST3 Human

Cystatin C is composed of 120 amino acids and has a molecular weight of approximately 13.3 kilodaltons . It plays a crucial role in inhibiting lysosomal proteinases, which are enzymes that break down proteins within lysosomes. By inhibiting these enzymes, cystatin C helps regulate protein turnover and prevents the breakdown of extracellular matrix proteins .

One of the most significant applications of cystatin C is as a biomarker for kidney function. It is filtered out of the bloodstream by the glomeruli in the kidneys. When kidney function declines, the levels of cystatin C in the blood increase, making it a reliable indicator of glomerular filtration rate (GFR) . Unlike creatinine, another common biomarker for kidney function, cystatin C levels are less influenced by factors such as age, gender, muscle mass, and diet .

Cystatin C has been extensively studied for its role in various medical conditions:

1. Kidney Disease: Elevated levels of cystatin C are associated with chronic kidney disease (CKD) and can be used to detect mild renal impairment .
2. Cardiovascular Disease: Research suggests that high cystatin C levels may predict new-onset or worsening cardiovascular disease .
3. Neurological Disorders: Cystatin C is also implicated in brain disorders involving amyloid deposition, such as Alzheimer’s disease .

Cystatin C offers several advantages over creatinine as a biomarker for kidney function:

• Independence from Muscle Mass: Unlike creatinine, cystatin C levels are not affected by muscle mass, making it a more accurate marker in individuals with varying muscle mass .
• Early Detection: Cystatin C can detect mild decreases in kidney function earlier than creatinine, which only rises after significant kidney damage has occurred .

Cystatin C was first isolated in 1961 as a cerebrospinal fluid-specific protein and was initially named gamma-trace protein . The complete amino acid sequence of human cystatin C was determined in 1981 by Grubb and Löfberg .