PEPTIDE ALDEHYDE INHIBITORS OF HEPATITIS-A VIRUS 3C PROTEINASE

Picornaviral 3C proteinases are a group of closely related thiol prote inases responsible for processing of the viral polyprotein into its co mponent proteins. These proteinases adopt a chymotrypsinlike fold [All aire et al, (1994) Nature 369, 72-77; Matthews et al, (1994) Cell 77, 761-771] and a display an active-site configuration like those of the serine proteinases, Peptide-aldehydes based on the preferred peptide s ubstrates for hepatitis A virus (HAV) 3C proteinase were synthesized b y reduction of a thioester precursor. Acetyl-Leu-Ala-Ala-(N,N'-dimethy lglutaminal) was found to be a reversible, slow-binding inhibitor for HAV 3C with a K-i of (4.2 +/- 0.8) x 10(-8) M. This inhibitor showed 50-fold less activity against the highly homologous human rhinovirus ( strain 14) 3C proteinase, whose peptide substrate specificity is sligh tly different, suggesting a high degree of selectivity, NMR spectromet ry of the adduct of the C-13-labeled inhibitor with the HAV-3C protein ase indicate that a thiohemiacetal is formed between the enzyme and th e aldehyde carbon as previously noted for peptide-aldehyde inhibitors of papain [Lewis & Wolfenden (1977) Biochemistry 16, 4890-4894; Gamcsi k et al, (1983) J, Am, Chem. Sec. 105, 6324-6325]. The adduct can also be observed by electrospray mass spectrometry.