proteolysis

Definition

Target type: biologicalprocess

The hydrolysis of proteins into smaller polypeptides and/or amino acids by cleavage of their peptide bonds. [GOC:bf, GOC:mah]

Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. It is a fundamental biological process that plays a crucial role in a wide range of cellular functions, including:

* **Protein turnover:** Cells constantly synthesize and degrade proteins to maintain a balance and adapt to changing conditions. Proteolysis removes damaged or misfolded proteins, regulates protein levels, and provides amino acids for new protein synthesis.
* **Signal transduction:** Proteolytic cleavage of proteins can generate active signaling molecules that trigger specific cellular responses. For example, the activation of many growth factors and hormones involves proteolytic processing.
* **Cell cycle regulation:** Proteolysis controls the progression of the cell cycle by degrading specific proteins, such as cyclins and cyclin-dependent kinases (CDKs), at appropriate times.
* **Apoptosis:** Programmed cell death, or apoptosis, involves the activation of proteases called caspases, which degrade key cellular components, leading to cell dismantling.
* **Digestion:** In the digestive system, proteases break down dietary proteins into smaller peptides and amino acids that can be absorbed by the body.

**Mechanism of Proteolysis:**

Proteolysis is carried out by enzymes called proteases (also known as peptidases). Proteases are highly specific enzymes that recognize and cleave peptide bonds in proteins. Different proteases have distinct substrate preferences and cleavage sites, resulting in diverse proteolytic events.

**Types of Proteases:**

Proteases can be classified into several groups based on their catalytic mechanism:

* **Serine proteases:** Utilize a serine residue in their active site for catalysis. Examples include trypsin, chymotrypsin, and elastase.
* **Aspartic proteases:** Employ an aspartic acid residue in their active site. Examples include pepsin and renin.
* **Cysteine proteases:** Use a cysteine residue for catalysis. Examples include papain and cathepsins.
* **Metalloproteases:** Require a metal ion (e.g., zinc) in their active site. Examples include thermolysin and matrix metalloproteinases (MMPs).

**Regulation of Proteolysis:**

Proteolytic activity is tightly regulated to ensure proper protein turnover and prevent uncontrolled protein degradation. Regulation can occur at multiple levels:

* **Protein synthesis and degradation rates:** The rates of protein synthesis and degradation are tightly balanced to maintain cellular homeostasis.
* **Protease expression and activation:** Proteases are often synthesized as inactive precursors (zymogens) and are activated by specific proteolytic events or cellular signals.
* **Protease inhibitors:** Specific inhibitors can bind to and block the active site of proteases, preventing their activity.

**Disorders and Diseases:**

Disruptions in proteolysis can lead to various disorders and diseases, including:

* **Cancer:** Deregulation of proteolysis can promote tumor growth and metastasis.
* **Neurodegenerative diseases:** Impaired protein degradation can contribute to the accumulation of misfolded proteins that are associated with Alzheimer's disease, Parkinson's disease, and Huntington's disease.
* **Inflammatory diseases:** Proteases can play a role in the inflammatory response and can contribute to chronic inflammatory conditions.

Proteolysis is a vital process that plays a critical role in numerous cellular functions. It is a complex and tightly regulated process that involves diverse enzymes, substrates, and regulatory mechanisms. Understanding the intricacies of proteolysis is essential for comprehending normal cellular function and for developing strategies to treat diseases associated with proteolytic dysfunction.'
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Proteins (170)

Compounds (1,936)