Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. NS2-3 protease (of hepatitis C virus, HCV) is an enzyme responsible for proteolytic cleavage between NS2 and NS3, which are structural proteins that form part of the HCV virus particle. NS3 protease of hepatitis C virus, on the other hand, is responsible for the cleavage of non-structural protein downstream. Both of these proteases are directly involved in HCV genome replication, that is, during the viral life-cycle that leads to virus multiplication in the host that has been infected by the virus.