Mechanism Governing the Cellular Susceptibility to Secretory Phospholipase A2 Mechanism Governing the Cellular Susceptibility to Secretory Phospholipase A2

by Jensen, Lauren Blackburn

Abstract (Summary)
Secretory phospholipase A2 (sPLA2) is an important part of apoptosis and disposal of damaged and dying cells. However, healthy cells are not susceptible to attack by sPLA2. Recent studies have focused on membrane properties necessary to induce susceptibility in both artificial and biological membranes. Hydrolysis of phospholipids by sPLA2 requires at least two preliminary steps: first, adsorption of the enzyme to the cellular membrane, and second, movement of a phospholipid into the active site of the enzyme. We determined the effects of susceptibility on each of the two steps and determined the contributions changing the equilibrium constants have on susceptibility. The equilibrium constant for step one increased by a factor of 2 during susceptibility, while the equilibrium constant for step two increased by a factor of 4. The rise in the second equilibrium constant caused the majority of the change in hydrolysis rate seen during susceptibility; the influence of the first equilibrium constant is minimal. We confirmed these results with adsorption studies (assessment of the first step). We additionally found that sPLA2 has a high affinity for the cellular membrane and that only a small percentage (3-5%) of the membrane is covered when all adsorption sites are filled by the enzyme. We proposed a mathematical model describing the mechanism of action of sPLA2, and we were able to experimentally justify the assumptions made in the model.
Bibliographical Information:


School:Brigham Young University

School Location:USA - Utah

Source Type:Master's Thesis

Keywords:secretory phospholipase a2 spla2 equilibrium constants membrane structure adsorption quantification


Date of Publication:06/10/2004

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