Cystatin
Cystatin is a type of protein that is known for its ability to inhibit cysteine proteases, which are enzymes that break down proteins and peptides. Cystatins are present in a wide variety of organisms and tissues, and they play a crucial role in numerous biological processes.
Function[edit | edit source]
Cystatins function primarily as inhibitors of cysteine proteases, which are enzymes that degrade proteins and peptides. These proteases are involved in a variety of biological processes, including protein recycling, digestion, and the immune response. By inhibiting these enzymes, cystatins help to regulate these processes and prevent excessive protein degradation.
Structure[edit | edit source]
Cystatins are typically small proteins, usually consisting of around 100 amino acids. They have a characteristic structure that includes two alpha helices and a five-stranded antiparallel beta sheet. This structure allows them to bind to and inhibit the active sites of cysteine proteases.
Types[edit | edit source]
There are several types of cystatins, which are classified based on their structure and function. These include:
- Type 1 cystatins: Also known as stefins, these are intracellular proteins that are found in all mammalian tissues.
- Type 2 cystatins: These are secreted proteins that are found in various body fluids, such as saliva and seminal fluid.
- Type 3 cystatins: Also known as kininogens, these are larger proteins that are involved in blood coagulation and inflammation.
Clinical significance[edit | edit source]
Cystatins have been implicated in a variety of diseases, including cancer, neurodegenerative diseases, and infectious diseases. For example, alterations in cystatin levels have been observed in patients with Alzheimer's disease, suggesting a potential role in the disease process. In addition, cystatins may have potential as therapeutic targets in the treatment of these diseases.
See also[edit | edit source]
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Contributors: Prab R. Tumpati, MD