Leupeptin

Leupeptin is a naturally occurring tripeptide aldehyde isolated from Actinomycetes that serves as a potent inhibitor of serine and cysteine proteases. The C-terminal aldehyde group forms a reversible covalent hemiacetal adduct with the active site serine or thiohemiacetal with active site cysteine, providing competitive inhibition of diverse proteases.

The compound inhibits trypsin-like serine proteases, calpains, cathepsins B, H, and L, and papain-family cysteine proteases. This broad specificity makes leupeptin invaluable for cell biology research where protection of proteins from endogenous proteolysis is essential during cell lysis and protein extraction.

Leupeptin is a standard component of protease inhibitor cocktails used during protein purification, immunoprecipitation, and cell lysate preparation. By preventing proteolytic degradation, it preserves native protein structure, post-translational modifications, and protein-protein interactions that would otherwise be lost.

Research applications extend to studying protease-dependent processes including autophagy, apoptosis, and protein quality control. Cell-permeable at higher concentrations, leupeptin can also be used to inhibit intracellular proteolysis in living cells, enabling investigation of protease function in cellular processes.