Displays three enzymatic activities: serine protease with a chymotrypsin-like fold, NTPase and RNA helicase. NS3 serine protease, in association with NS4A, is responsible for the cleavages of NS3-NS4A, NS4A-NS4B, NS4B-NS5A and NS5A-NS5B. The NS3/NS4A complex prevents phosphorylation of host IRF3, thus preventing the establishment of dsRNA induced antiviral state. The NS3/NS4A complex induces host amino acid transporter component SLC3A2, thus contributing to HCV propagation. NS3 RNA helicase binds to RNA and unwinds both dsDNA and dsRNA in the 3' to 5' direction, and likely resolves RNA complicated stable secondary structures in the template strand. Binds a single ATP and catalyzes the unzipping of a single base pair of dsRNA. Inhibits host antiviral proteins TBK1 and IRF3 thereby preventing the establishment of an antiviral state. Cleaves host MAVS/CARDIF thereby preventing the establishment of an antiviral state. Cleaves host TICAM1/TRIF, thereby disrupting TLR3 signaling and preventing the establishment of an antiviral state 