KINETIC STUDIES OF SOLVENT EFFECTS ON THE REGULATION OF HUMAN EPITHELIAL 15-LIPOXYGENASE-2 (15-LOX-2)

Abstract

Lipoxygenases (LOXs) are non-heme, iron containing enzymes that catalyze the oxidation of polyunsaturated fatty acids, resulting in the formation of potent bioactive cell signaling molecules.15-Lipoxygenase-2 (15-LOX-2), one of six human lipoxygenase enzymes, plays an important role in homeostasis and is implicated in the formation of atherosclerotic plaques, a contributor to cardiovascular disease. 15-LOX-2 is structurally solved and has well characterized kinetic isotope effects reported for its natural substrate, arachidonic acid (AA), which revealed the initial hydrogen transfer as rate-limiting for the reaction. Accumulating evidence has suggested that conformational fluctuations of a protein may mediate hydrogen transfer processes. Conformational motions can be influenced by solvent effects. Viscogens, such as trehalose and glucose, along with pH and temperature changes can be used to test solvent effects on the conformational fluctuations of a protein. The kinetic and structural studies of the 15-LOX-2 reaction with AA indicate that the reaction is inhibited in a concentration dependent manner by the viscogens trehalose and glucose. The kinetic investigations conducted provide insight into the roles of solvent layers in LOX-catalyzed reactions and act as a bridge for future investigations on the impact of large-scale conformational changes on 15-LOX-2 membrane binding interactions.