Figure 1. Mechanism of Action of Acyclovir

In this HSV-infected human cell, the acyclovir molecules enter the cell and are converted to acyclovir monophosphate by the HSV enzyme thymidine kinase (TK). Enzymes in the human cell add two more phosphates to eventually form the active drug acyclovir triphosphate. The acyclovir triphosphate competes with 2-deoxyguanosine triphosphate (dGTP) as a substrate for viral DNA polymerase, as well as acting as a chain terminator. In actual infection, the HSV releases its naked capsid that delivers DNA to the human nucleus; the active drug acyclovir triphosphate exerts its action on the viral DNA located in the nucleus.

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