Enzyme

Active site

Stereochemistry

Allosteric regulation

Chemistry

Nordihydroguaiaretic acid

Arachidonic acid

Lipoxygenase

Biochemistry

Arachidonate 5-lipoxygenase

Nature Chemical Biology

Leukotrienes (LT) are lipid mediators of the inflammatory response that are linked to asthma and atherosclerosis. LT biosynthesis is initiated by 5-lipoxygenase (5-LOX) with the assistance of the substrate-binding 5-LOX-activating protein at the nuclear membrane. Here, we contrast the structural and functional consequences of the binding of two natural product inhibitors of 5-LOX. The redox-type inhibitor nordihydroguaiaretic acid (NDGA) is lodged in the 5-LOX active site, now fully exposed by disordering of the helix that caps it in the apo-enzyme. In contrast, the allosteric inhibitor 3-acetyl-11-keto-beta-boswellic acid (AKBA) from frankincense wedges between the membrane-binding and catalytic domains of 5-LOX, some 30 Å from the catalytic iron. While enzyme inhibition by NDGA is robust, AKBA promotes a shift in the regiospecificity, evident in human embryonic kidney 293 cells and in primary immune cells expressing 5-LOX. Our results suggest a new approach to isoform-specific 5-LOX inhibitor development through exploitation of an allosteric site in 5-LOX.                                                                  Structures of 5-lipoxygenase (5-LOX) reveal that NDGA disturbs regions that shield the active site while AKBA binds an allosteric site. NDGA inhibits 5-LOX activity using its redox-active function, while AKBA changes the enzyme’s regiospecificity

Structural and mechanistic insights into 5-lipoxygenase inhibition by natural products