Activation of 11R-Lipoxygenase Is Fully Ca2+-Dependent and Controlled by the Phospholipid Composition of the Target Membrane

Activation of some lipoxygenases (LOX) is found to be related to the selective membrane binding upon cell stimulation. In this study, a systematic analysis of the effect of the lipid composition on the membrane binding efficiency, Ca2+ affinity, and enzymatic activity of 11R-LOX was performed. The analysis of the membrane targeting by fluorometric and surface plasmon resonance measurements in the absence of Ca2+ showed an exclusive binding of 11R-LOX to the anionic phospholipids (phosphatidylinositol < phosphatidylglycerol approximate to phosphatidylserine) containing model membranes. The presence of Ca2+ enhanced the rate of interaction and influenced its mode. The modulation of the activity of 11R-LOX indicated that (i) Ca2+ binding is a prerequisite for productive membrane association, (ii) the reaction of 11R-LOX with arachidonic acid coincided with and was driven by its Ca2+-mediated membrane association, and (iii) phosphatidylethanolamine and anionic phospholipids had a synergistic effect on the Ca2+ affinity, in line with a target-activated messenger affinity mechanism [Corbin, J. A., et al. (2007) Biochemistry 46, 4322-4336]. According to the mechanism proposed in this report, 11R-LOX can bind to the membranes in two different modes and the efficiency of productive membrane binding is determined by a concerted association of Ca2+ and lipid headgroups.