Caspase

Caspases are cysteine proteases that cleave target proteins after aspartate residues. They regulate programmed cell death, inflammation, and other cellular processes.

Caspase activation: The conversion of inactive procaspases into active proteases through cleavage, assembly, or both. Initiator caspases activate downstream caspases through cleavage and proximity-driven assembly.
Cysteine protease: A protease that uses a cysteine residue in its active site to cleave peptide bonds. Caspases belong to this enzyme class and use catalytic cysteine for protein cleavage.
Caspase assay: A laboratory test that measures caspase activity or detects caspase cleavage products. These assays quantify caspase activation in cells, tissues, and experimental systems.
Caspase-3: An executioner caspase that cleaves many cellular proteins during apoptosis. Its substrate cleavage produces hallmark structural changes in apoptotic cells.
Caspase substrate specificity: The sequence and structural preferences that determine which proteins a caspase cleaves. Shared cleavage preferences do not fully explain why caspases target distinct proteins in cells.
Procaspase: An inactive precursor protein that can be converted into an active caspase. Most caspases are produced as procaspases, limiting unwanted proteolysis before activation.
Proteolysis: The enzymatic breakdown of proteins into smaller peptides or amino acids. Caspases produce their effects by selectively proteolyzing cellular proteins.
Caspase inhibitor: A molecule that reduces caspase activity by binding the enzyme or interfering with its activation. Inhibitors help test whether caspases cause an observed cellular effect.
Caspase-8: An initiator caspase that transmits death-receptor signals and regulates other cell-death pathways. It initiates extrinsic apoptosis and can restrain necroptosis.
Caspase non-apoptotic functions: Caspase activities that regulate processes other than cell death, including differentiation and immune signaling. These functions complicate the assumption that caspase activation always commits a cell to die.

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