Proteolytic Enzymes, Substrates and Inhibitors

Proteolytic enzymes, or proteases, break down peptide bonds of proteins. They are classified into 6 groups: serine, threonine, cysteine, aspartate, glutamic proteases, and metalloproteases.

Apoptosis caspases are a family of cysteine proteases. They form a cascade that cleave downstream inactive pro-caspases into an active form and eventually digest protein substrates in apoptotic cells. Caspase inhibitors bind to the active site of caspases either in a reversible or irreversible manner. Inhibitors include a peptide recognition sequence attached to a functional group, such as an aldehyde (CHO), chloromethylketone (CMK), or fluoromethylketone (FMK). The peptide recognition sequence determines the specificity of a particular caspase.