Small-molecule inhibitor: Ac-Trp-Glu-His-Asp-H

Name

History: A study of the specificity of caspase-1 with a positional-scanning substrate library led to the identification of Trp-Glu-His-Asp as the preferred site of cleavage, and this formed the basis for the design of the inhibitor Ac-Trp-Glu-His-Asp-H (Rano et al., 1997).
Peptidases inhibited: Ac-Trp-Glu-His-Asp-H is a very potent inhibitor of caspase-1 (K_i 56 pM: Rano et al., 1997).
Mechanism: Inhibition is reversible.

Structure
Chemical/biochemical name: N-acetyl-tryptophanyl-glutamyl-histidinyl-aspartaldehyde

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).