BIOPHYSICAL THEORY AND MODELING |
CHANGES OF ENZYME ACTIVITY IN LIPID SIGNALING PATHWAYS RELATED TO SUBSTRATE REORDERING
Dino G. Salinas 1*, Milton de la Fuente 2 and Juan G. Reyes 3
1 Universidad Diego Portales
2 Universidad de Chile
3 Pontificia Universidad Católica de Valparaíso
* To whom correspondence should be addressed. E-mail: dino.salinas{at}udp.cl.
Submitted on December 1, 2004
Revised on January 18, 2005
Accepted on 9 May 2005
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Abstract |
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The static fluid mosaic model of biological membranes has been progressively complemented by a dynamic membrane model that includes phospholipid reordering in domains that are proposed to extend from nanometers to microns. Kinetic models for lipolytic enzymes have only been developed for homogeneous lipid phases. In this work, we develop a generalization of the well known Surface Dilution Kinetic Theory to cases where, in a same lipid phase, both domain and non-domain phases coexist. Our model also allows understanding the changes in enzymatic activity due to a decrease of free substrate concentration when domains are induced by peptides. This lipid reordering and domain dynamics can affect the activity of lipolytic enzymes, and can provide a simple explanation for how basic peptides, with a strong direct interaction with acidic phospholipids (such as 
-amyloid peptide), may cause a complex modulation of the activities of many important enzymes in lipid signaling pathways.
Key Words:
cationic peptides, enzyme kinetics, lipid rafts
