Sakaguchi Akira

Inhibition by a novel azole antifungal agent with a geranyl group on lanosterol 14α-demethylase of yeast

Abstract AFK-108 (1-[2-(2,4-dichlorophenyl)-2-((2E)-3,7-dimethylocta-2,6-dienyloxy)ethyl]-1H-imidazole) is a new imidazole derivative characterized by a geranyl substituent showing strong antifungal activity. Azole antifungal agents are known to be potent inhibitors of lanosterol 14α-demethylase (P45014DM) of fungi. The role of the geranyl group of AFK-108 on interaction of AFK-108 with the target was studied by using Saccharomyces cerevisiae P45014DM as the model enzyme. AFK-108 and some of its derivatives bound to oxidized P45014DM with one-to-one stoichiometry and inhibited the demethylase activity. AFK-108 derivatives having the longer farnesyl or the shorter prenyl group showed lower affinity than AFK-108 for the enzyme. AFK-108 caused 100% inhibition at the equivalent concentration to P45014DM in the reaction mixture (0.07 μM), while the farnesyl derivative inhibited the activity by 60% at the same concentration. AFK-108 interfered with the binding of CO to the ferrous P45014DM. However, the interfering effect of the prenyl derivative was lower than that of AFK-108. Another AFK-108 derivative having the saturated 3,7-dimethyloctyl group was also a weaker inhibitor than AFK-108. These experiments suggest that the geranyl group of AFK-108 interacts with the substrate binding site of P45014DM that recognises the side chain of the substrate. AFK-108 is the first example of an azole derivative interacting with the side chain recognising region of the substrate binding site of P45014DM.