Analysis Note

Leupeptin gives multiple peaks on HPLC due to equilibria among three forms in solution. Purity determined using three main peaks. Majority of contaminating peptide is racemized leupeptin.

Biochem/physiol Actions

Inhibitor of serine and cysteine proteases. Inhibits plasmin, trypsin, papain, calpain, and cathepsin B. Does not inhibit pepsin, cathepsins A and D, thrombin, or α-chymotrypsin. Effective concentration 10-100 µM. There have been numerous studies using leupeptin to protect against hearing loss caused by acoustic overstimulation or the ototoxic antibiotic gentamicin. (Loss of cochlear hair cells is believed to be mediated by calpain.)

General description

Leupeptin, or N-acetyl-L-leucyl-L-leucyl-L-argininal, is a naturally occurring tripeptide that acts particularly as a serine protease inhibitor and as a cysteine protease inhibitor. Its mechanism of action involves structurally similar covalent binding reactions:•In the active site of serine proteases, leupeptin forms a covalent hemiacetal adduct between the aldehyde group of leupeptin and the hydroxyl group of a serine residue in the enzyme active site.•In the active site of cysteine proteases, the electrophilic (aldehyde) carbon of leupeptin forms a comparable bond with the sulfur atom of a cysteine residue in the enzyme active site.

Packaging

5, 10, 25, 50, 100, 250 mg in glass bottle