calcium-dependent cysteine-type endopeptidase activity

Definition

Target type: molecularfunction

Catalysis of the hydrolysis of nonterminal peptide bonds in a polypeptide chain by a mechanism using a cysteine residue at the enzyme active center, and requiring the presence of calcium. [GOC:mah]

Calcium-dependent cysteine-type endopeptidase activity is a molecular function that involves the enzymatic cleavage of peptide bonds within proteins. This activity is specifically characterized by its dependence on calcium ions (Ca2+) for optimal function and its use of a cysteine residue as the catalytic nucleophile within the active site of the enzyme.

**Key Features:**

- **Calcium Dependence:** Calcium ions play a crucial role in the activity of these enzymes by binding to specific sites on the protein, often within the active site. This binding event induces conformational changes that are essential for proper substrate recognition and catalysis.

- **Cysteine Nucleophile:** The active site of these endopeptidases contains a cysteine residue that acts as the nucleophile in the catalytic process. The sulfur atom of the cysteine side chain attacks the carbonyl carbon of the peptide bond, forming a covalent intermediate.

- **Hydrolysis:** Following the nucleophilic attack, the covalent intermediate is hydrolyzed by the addition of a water molecule. This step results in the cleavage of the peptide bond and the release of the cleaved peptide fragments.

**Biological Significance:**

Calcium-dependent cysteine-type endopeptidases are involved in a wide range of biological processes, including:

- **Proteolysis:** These enzymes contribute to the breakdown of proteins, playing a critical role in protein turnover, degradation of damaged or misfolded proteins, and activation of specific proteins by proteolytic processing.

- **Signal Transduction:** Some of these enzymes act as signaling molecules, participating in cellular communication pathways. They can cleave and activate or deactivate other proteins involved in signaling cascades.

- **Apoptosis:** These endopeptidases can be involved in programmed cell death (apoptosis) by cleaving proteins that are essential for cell survival, contributing to the disassembly and dismantling of the cell.

- **Development:** These enzymes are important during development, regulating cell differentiation and tissue morphogenesis.

**Examples:**

Examples of calcium-dependent cysteine-type endopeptidases include:

- **Calpains:** A family of cysteine proteases that are involved in a wide range of cellular processes, including muscle protein breakdown, cell signaling, and apoptosis.
- **Caspases:** A family of cysteine proteases that play a central role in apoptosis by cleaving specific proteins that regulate cell death pathways.
- **Cathepsins:** A group of lysosomal cysteine proteases that are involved in protein degradation within the lysosomes, contributing to intracellular protein turnover.

**Therapeutic Implications:**

The importance of calcium-dependent cysteine-type endopeptidases in various biological processes has led to their investigation as potential therapeutic targets for a range of diseases, including cancer, neurodegenerative diseases, and inflammatory disorders.

**Inhibitors:**

Specific inhibitors of these enzymes have been developed for both research and therapeutic purposes. These inhibitors can block the activity of these enzymes, potentially preventing or mitigating the pathological consequences associated with their dysregulation.'
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Proteins (5)

Compounds (25)