Biophys J, February 2001, p. 565-578, Vol. 80, No. 2

Changes in a Phospholipid Bilayer Induced by the Hydrolysis of a Phospholipase A₂ Enzyme: A Molecular Dynamics Simulation Study

Marja T. Hyvönen,^* Katariina Öörni, Petri T. Kovanen, and Mika Ala-Korpela

 ^*NMR Research Group, Department of Physical Sciences, University of Oulu, FIN-90014 Oulu, Finland, and  Wihuri Research Institute, FIN-00140 Helsinki, Finland

Phospholipase A₂ (PLA₂) enzymes are important in numerous physiological processes. Their function at lipid-water interfaces is also used as a biophysical model for protein-membrane interactions. These enzymes catalyze the hydrolysis of the sn-2 bonds of various phospholipids and the hydrolysis products are known to increase the activity of the enzymes. Here, we have applied molecular dynamics (MD) simulations to study the membrane properties in three compositionally different systems that relate to PLA₂ enzyme action. One-nanosecond simulations were performed for a 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLPC) bilayer and for two of its PLA₂-hydrolyzed versions, i.e., bilayers consisting of lysophospholipids and of either free charged linoleate or free uncharged linoleic acid molecules. The results revealed loosening of the structure in the hydrolyzed bilayer due to increased mobility of the molecules in the direction normal to the bilayer. This loss of integrity due to the hydrolysis products is in accord with observations that not only the presence of hydrolysis products, but also a variety of other perturbations of the membrane may activate PLA₂. Additionally, changes were observed in other structural parameters and in the electrostatic potential across the membrane-water interface. These changes are discussed in relation to the simulation methodology and the experimental observations of PLA₂-hydrolyzed membranes.

Biophys J, February 2001, p. 565-578, Vol. 80, No. 2
© 2001 by the Biophysical Society   0006-3495/01/02/565/14  $2.00

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