Small-molecule inhibitor: DANLME

Name

History: DANLME was discovered as an inhibitor of pepsin by Rajagopalan et al. (1966).
Peptidases inhibited: DANLME has been used as a general inhibitor of peptidases in family A1, and enzymes affected include pepsin, cathepsin D and cathepsin E. Aspergilloglutamic peptidase also is inhibited (Chang et al., 1976). Physarolisin, an unusual serine peptidase with an essential carboxyl group, is inhibited, although most members of family S53 are not (Nishii et al., 2003). Thermopsin is slowly and incompletely inactivated by DANLME, so it is not clear whether DANLME reacts with a catalytic residue or not (Fusek et al., 1990).
Mechanism: DANLME reacts much more rapidly and specifically with pepsin in the presence of Cu²⁺ ions than in their absence, and it is clear that it is a DANLME-copper complex that is the effective inhibitor (Rajagopalan et al., 1966; Lundblad & Stein, 1969). Although the compound was designed to be a substrate analogue, that is not necessary, as diazoacetylglycine ethyl ester inhibits as well as the norleucine derivative (in the presence of Cu²⁺ (Lundblad & Stein, 1969). The inhibited pepsin is an ester, and the inhibitor is released by hydroxylamine.

Structure
Chemical/biochemical name: diazoacetyl norleucine methyl ester
Related inhibitors: Some other diazoacetyl compounds, including diazoacetylglycine ethyl ester, react similarly. A coloured analogue, N-diazoacetyl-N"-(2,4-dinitrophenyl)-ethylenediamine has been used to label the active site residue in nepenthesin (A01.040: Lobareva et al., 1973).