Small-molecule inhibitor: Z-Leu-Leu-Leu-ketoaldehyde

Name

History: BzLLLCOCHO was first described as an inhibitor of the chymotrypsin-like activity of the proteasome by Lynas et al. (1998).
Peptidases inhibited: BzLLLCOCHO inhibits all three major peptidase activities of the proteasome, the peptidyl-glutamyl peptidase activity of catalytic subunit 1, the trypsin-like activity of subunit 2 and the chymotrypsin-like activity of catalytic subunit 3 (Crawford et al., 2006).
Mechanism: Inhibition is slow, tight-binding reversible, with K_i about 3 nM (Lynas et al., 1998).

Inhibitor class: This is a compound of the aldehyde class. The discovery of leupeptin in the late 1960s drew attention to the potential of aldehydes as peptidase inhibitors, and the inhibition of papain by synthetic aldehydes was further studied by Wolfenden and co-workers (e.g. Westerik & Wolfenden, 1972). Many aldehydes are now known as inhibitors of serine, cysteine or threonine peptidases. They form hemiacetal or thiohemiacetal conjugates with the essential hydroxyl or thiol group of the enzyme that are transition state analogues (Bendall et al., 1977). The compounds exist predominantly in their hydrated forms in aqueous solution, but only the aldehyde is an effective inhibitor (Bendall et al., 1977). Peptide aldehydes and semicarbazones are valuable ligands for affinity chromatography of serine and cysteine peptidases (Rich et al., 1986; Dando & Barrett, 1992). Aldehydes can also act as inhibitors of metallopeptidases (Strater & Lipscomb, 1995).
Comment: This is a tripeptide-like, alpha-keto aldehyde, or glyoxal.
Reviews: Crawford et al. (2006)