Mechanism Governing the Cellular Susceptibility to Secretory Phospholipase A2

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.

Name thesis:degree_name

MS

Grantor dc:publisher

Brigham Young University - Provo

Author dc:creator

• Jensen, Lauren Blackburn

• secretory phospholipase A2
• sPLA2
• equilibrium constants
• membrane structure
• adsorption
• quantification
• Cell and Developmental Biology
• Physiology

Language dc:language

English

Repository record dc:identifier

https://scholarsarchive.byu.edu/etd/1137

OAI identifier oai:identifier

oai:scholarsarchive.byu.edu:etd-2136