Mechanistic studies of electrophilic protease inhibitors of full length hepatic C virus (HCV) NS3

Figures & data

Figure 1 A schematic representation of the active site of HCV NS3 and its interaction with non-electrophilic and electrophilic inhibitors, assuming typical serine protease inhibition mechanisms. (A) mechanism-based inhibition by compounds with a C-terminal electron withdrawing group (EWG), and (B) product-based inhibitors with C-terminal carboxyl groups.

Table I.  Inhibition of HCV NS3 by electrophilic and non-electrophilic inhibitors at different pH and ionic strengths^†.

		Ki (μM)^‡
		pH 6.0		pH 8.0
		NaCl (mM)
Inhibitor	P1	0	100	0	100
Electrophilic and non-acidic
Abu PFK*		0.084 ± 0.008	0.15 ± 0.03	0.082 ± 0.007	0.051 ± 0.003
Nva PFK*		0.15 ± 0.01	0.35 ± 0.06	0.145 ± 0.018	0.117 ± 0.011
ACPC PFK		1.49 ± 0.08	3.2 ± 0.8	4.1 ± 0.15	1.68 ± 0.16
Electrophilic and acidic
Nva KT*		0.134 ± 0.009	0.46 ± 0.1	1.74 ± 0.09	1.88 ± 0.14
ACPC KT		0.37 ± 0.02	1.07 ± 0.26	5.62 ± 0.37	2.27 ± 0.23
ACPC KA		0.052 ± 0.003	0.19 ± 0.03	3.77 ± 0.21	1.82 ± 0.13
Non-electrophilic and acidic
Abu COOH		0.098 ± 0.007	0.25 ± 0.044	2.75 ± 0.02	1.25 ± 0.08
Nva COOH		0.016 ± 0.001	0.031 ± 0.006	0.45 ± 0.006	0.245 ± 0.018
ACPC COOH		0.0062 ± 0.00009	0.025 ± 0.0045	0.32 ± 0.017	0.2 ± 0.01

* Stereocenters next to electrophilic carbonyls are assumed to be racemized in the assay buffer

^† R = Acetyl for Abu COOH [22], all other compounds have R = succinyl [16]

^‡ These K_i values differ slightly from those published previously [16,22] due to differences in buffer composition and pH.

Figure 2 Dependence of the kinetic constants of HCV NS3 on pH. A) V_max and B) K_m as a function of pH, at low (•) and high (▪) ionic strength.

Figure 3 Effect of pH and NaCl concentrations on the inhibition constants for different inhibitors. A) Overview of K_i values for all compounds and conditions, see Table I for details, B) Ratio of K_i^{pH 8.0}/K_i^{pH 6.0} at 0 mM NaCl (grey) and 100 mM NaCl (black). C) Ratio of K_i^{100 mM NaCl}/K_i^{0 mM NaCl} at pH 6.0 (grey) and pH 8.0 (black).

Oscarsson K, Poliakov A, Oscarson S, Danielson UH, Hallberg A, Samuelsson B. Peptide-based inhibitors of hepatitis C virus full-length NS3 (protease-helicase/NTPase): Model compounds towards small molecule inhibitors. Bioorg Med Chem 2003; 11(13)2955–2963

 PubMed Web of Science ®Google Scholar

Johansson A, Poliakov A, Åkerblom E, Wiklund K, Lindeberg G, Winiwarter S, Danielson UH, Samuelsson B, Hallberg A. Acyl sulfonamides as potent protease inhibitors of the hepatitis C virus full-length NS3 (protease-helicase/NTPase). A comparative study of different C-terminals. Bioorg Med Chem 2003; 11: 2551–2568

 PubMed Web of Science ®Google Scholar