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Synthetic depsipeptide substrates for the assay of human hepatitis C virus protease
E Bianchi1, C Steinkühler, M Taliani
1Istituto di Ricerche di Biologia Molecolare P. Angeletti (IRBM), Via Pontina Km 30,600, Rome, Italy.
Insights
Researchers developed improved ester substrates for Hepatitis C virus (HCV) NS3 protease assays. These depsipeptides enhance enzyme activity detection, aiding antiviral drug development for the 50 million worldwide infected.
Area of Science:
- Biochemistry
- Virology
- Drug Discovery
Background:
- Hepatitis C virus (HCV) causes significant global liver disease, with millions chronically infected.
- The HCV NS3 protease is a key target for antiviral therapies.
- Existing synthetic peptide substrates for NS3 protease assays have limitations due to low efficiency.
Purpose of the Study:
- To develop a sensitive and efficient in vitro assay for Hepatitis C virus NS3 protease activity.
- To identify improved substrate designs for studying NS3 protease biochemistry and developing inhibitors.
Main Methods:
- Solid-phase synthesis of novel depsipeptide substrates replacing amide bonds with ester linkages.
- Characterization of the kinetic properties (kcat/Km) of the NS3 protease using these ester substrates.
Main Results:
- Depsipeptide substrates demonstrated over 100-fold improvement in kcat/Km values compared to traditional peptide substrates.
- Achieved kinetic efficiencies up to 13,000 M-1 s-1.
- Enabled sensitive detection of NS3 protease activity with subnanomolar enzyme concentrations.
Conclusions:
- Ester-modified depsipeptides are highly effective substrates for Hepatitis C virus NS3 protease assays.
- This advancement facilitates detailed biochemical studies and inhibitor screening for HCV drug development.
- Solid-phase synthesis offers a practical route to these improved substrates.
Abstract:
Hepatitis C virus (HCV) is the major etiological agent of both parenterally transmitted and sporadic non-A, non-B hepatitis. The disease is a major health problem with an estimated 50 million people infected worldwide, a high percentage of whom become chronically infected and are at high risk for liver cirrhosis. The serine protease contained within the N-terminal region of the nonstructural protein 3 (NS3 protease) of HCV is considered a promising target for the development of an antiviral therapy. A prime requisite to study in detail the biochemistry of the protease as well as develop inhibitors is the availability of a fast and sensitive in vitro assay of enzyme activity. However, due to their low kcat/Km values, synthetic peptide substrates based on the natural cleavage sites appear unsuitable for this purpose. We show here that appropriate substrates can be obtained by substituting the scissile amide bond with an ester linkage. The resulting depsipeptides show >100-fold improvement in kcat/Km values, up to 13,000 M-1 s-1, enabling detection of activity with subnanomolar NS3 concentrations. The ester substrates are obtained in high yield entirely by solid-phase synthesis using commercially available materials, without the need for any preassembled building blocks.(c) 1996 Academic Press, Inc.