Kinetics of enzymatic reactions in lipid membranes containing domains.
An appreciable part of enzymes operating in vivo is associated with lipid membranes. The function of such enzymes can be influenced by the presence of domains containing proteins and/or composed of different lipids. The corresponding experimental model-system studies can be performed under well controlled conditions, e.g., on a planar supported lipid bilayer or surface-immobilized vesicles. To clarify what may happen in such systems, we propose general kinetic equations describing the enzyme-catalyzed substrate conversion occurring via the Michaelis-Menten (MM) mechanism on a membrane with domains which do not directly participate in reaction. For two generic situations when a relatively slow reaction takes place primarily in or outside domains, we take substrate saturation and lateral substrate-substrate interactions at domains into account and scrutinize the dependence of the reaction rate on the average substrate coverage. With increasing coverage, depending on the details, the reaction rate reaches saturation via an inflection point or monotonously as in the conventional MM case. In addition, we show analytically the types of reaction kinetics occurring primarily at domain boundaries. In the physically interesting situation when the domain growth is fast on the reaction time scale, the latter kinetics are far from conventional. The opposite situation when the reaction is fast and controlled by diffusion has been studied by using the Monte Carlo technique. The corresponding results indicate that the dependence of the reaction kinetics on the domain size may be weak.
Division of Biological Physics, Department of Applied Physics, Chalmers University of Technology, SE-41296 Göteborg, Sweden. Boreskov Institute of Catalysis, Russian Academy of Sciences, Novosibirsk 630090, Russia.
Vladimir P
VP
Zhdanov
Fredrik
F
Höök
D022162:Cytoplasmic Vesicles / Q000737:chemistry / Q000378:metabolism*; D004058:Diffusion; D004798:Enzymes / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism*; D021962:Membrane Microdomains / Q000737:chemistry* / Q000378:metabolism; D008962:Models, Theoretical; D009010:Monte Carlo Method
D004798:Enzymes; D008051:Lipid Bilayers