Lapachol inhibition of DT-diaphorase (NAD(P)H:quinone dehydrogenase)

Lapachol has been found to be a potent inhibitor of the enzyme DT-Diaphorase. Inhibition is competitive versus NADH, Ki = 0.15 microM. Lapachol was not a good substrate for cytochrome P450 reductase, thus inhibition of DT-Diaphorase should not promote its metabolism via radical generating pathways. DT-Diaphorase has been used to test a lapachol affinity chromatography column designed for purification of another coumarin anticoagulant and lapachol sensitive enzyme, vitamin K epoxide reductase.