beta-lactones as a new class of cysteine proteinase inhibitors: Inhibitionof hepatitis a virus 3C proteinase by N-Cbz-serine beta-lactone

[GRAPHICS] N-Benzyloxycarbonyl-L-serine beta-lactone (1) is shown to irreversibly inac tivate the 3C cysteine proteinase of hepatitis A virus (HAV) with k(inact) = 0.70 min(-1), K-I = 1.84 x 10(-4) M and k(inact)/K-I = 3800 M-1 min(-1) a t an enzyme concentration of 0.1 mu M. Mass spectrometric and HMQC NMR stud ies using C-13-labeled 1 show that the active site cysteine (Cys-172) thiol of the HAV 3C proteinase attacks the beta-position (i.e, C-4) of the oxeta none ring, thereby leading to ring opening and alkylation of the sulfur, In contrast, the enantiomer of this beta-lactone, 2, is a reversible competit ive inhibitor (K-I = 1.50 x 10(-6) M) at similar enzyme concentrations. The beta-lactone motif represents a new class of inhibitors of cysteine protei nases.