Autoproteolysis

Autoproteolysis is the self-catalyzed cleavage of peptide bonds within a protein. It describes a process in which a polypeptide uses its own catalytic activity to cut one or more bonds in its own chain. Autoproteolysis can occur intramolecularly (cis) when a single molecule cleaves itself, or intermolecularly (trans) when one molecule cleaves another identical molecule. It is distinct from proteolysis by separate enzymes and can be part of normal maturation or a regulatory mechanism, or it may contribute to degradation under stress.

Mechanisms and triggers: Autoproteolytic events are governed by the structure and chemistry of the protein, including catalytic residues that become positioned to attack a nearby peptide bond. Conditions such as pH shifts, redox state, metal ions, or partial unfolding can reveal the scissile bond. In maturation processes, autoproteolysis removes inhibitory segments or generates active subunits from a precursor. In other cases, self-cleavage serves to regulate activity or mark a protein for controlled degradation.

Examples and scope: Autoproteolysis has been observed in a range of systems, including self-processing of precursor enzymes that activates proteolytic activity, and in some viral, bacterial, and cellular proteins that undergo self-cleavage during maturation or regulation. Some proteins also undergo self-cleavage as a part of regulated degradation. While autoproteolysis can be essential for function, aberrant self-cleavage can contribute to instability or disease.