Squalene epoxidase (SE) (EC 1.14.99.7) catalyzes the conversion of squalene to (3S)-2,3-oxidosqualene, a rate- limiting step of cholesterol biosynthesis.1 In addition to oxygen, vertebrate SE requires FAD, NADPH, NADPH- cytochrome P-450 reductase, and a supernatant protein factor. The nonmetallic flavin monooxygenase induces the splitting of the O-O bond, the insertion of one oxygen atom into the substrate (squalene), and reduction of the other to H2O via formation of flavin C(4a)-hydroperoxide (Figure
1).1 Since SE controls the throughput from squalene to
sterols in cholesterol biogenesis, enzyme inhibitors of SE have been potential targets for the design of cholesterol- lowering drugs. To date, several potent and specific SE enzyme inhibitors including chemically synthesized squalene analogues and allylamine derivatives have been developed, although there are as yet no successful reports of human clinical trials.