Topoisomerase Inhibitor. Camptothecin is an anti-cancer alkaloid that specifically inhibits DNA topoisomerase I and DNA topoisomerase II (topoisomerase I/II). The highly conserved region around Gly505 of the topoisomerase I was found to be important for camptothecin activity.
Camptothecin converts topoisomerase into a cell poison by trapping the cleavable covalent complex of enzyme with duplex DNA and blocking the re-ligation step. Thereby enhancing and stabilizing the formation of DNA breakage which is responsible for cell death.
Camptothecin inhibits (IC50= 30 nM) Tat protein-mediated transactivation of HIV-1 and enhances 10/PKC??alpha activity during apoptosis in HL60 myeloid leukemia cells via a caspase-regulated mechanism. Cell Signaling Activators and Inhibitors; Topoisomerase Inhibitors, Anticancer Compounds, Apoptosis Inducers.