Exploring allosteric properties of mammalian ALOX15: octyl (N-(4-(benzofuran-2-yl)-2-methoxyphenyl)sulfamoyl)- and octyl (N-(4-(1H-indol-2-yl)-2-methoxyphenyl)sulfamoyl)carbamates as ALOX inhibitors

Abstract

Mammalian ALOX15 are allosteric enzymes but the mechanism of allosteric regulation remains a matter of discussion. Octyl (N-(5-(1H-indol-2-yl)-2-methoxyphenyl)sulfamoyl)carbamate inhibits the linoleate oxygenase activity of ALOX15 at nanomolar concentrations, but oxygenation of arachidonic acid is hardly affected. The mechanism of substrate selective inhibition suggests inter-monomer communication within the allosteric ALOX15 dimer complex, in which the inhibitor binding to monomer A induces conformational alterations in the structure of the active site of monomer B. Interactions of the NH-group of the indole moiety with the Fe(III)–OH⁻ cofactor or of the SO₂ group of the sulfocarbamate moiety with the side chain NH₂ group of Gln596 may be important for proper inhibitor placement in the ALOX15 allosteric complex. Substitution of a H-bond donor to a H-bond acceptor (NH–O-exchange) impacts but does not eliminate the ability of the compound to inhibit preferentially the LA-oxygenase activity of ALOX15. In contrast, swapping the positions of CH₃O- and NH groups at the 2-aryl moiety led to a loss of substrate selective inhibition. In silico docking studies and molecular dynamics-simulations using a dimeric allosteric ALOX15 model have shown that binding of the substrate molecule to ALOX15 monomer B may alter the structure of the monomer A-inhibitor complex forcing the inhibitor to adopt a different binding mode. Taken together, this data suggests the possibility of two-way communication between ALOX15 monomers during enzymatic catalysis.