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-((2 E)-3,7-dimethylocta-2,6-dienyloxy)ethyl]-1 H-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 (P450 14DM) 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 P450 14DM as the model enzyme. AFK-108 and some of its derivatives bound to oxidized P450 14DM 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 P450 14DM 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 P450 14DM. 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 P450 14DM 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 P450 14DM.