Regulation of Membrane Fluidity by Lipid Desaturases
It has long been known that normal prokaryotic as well as eukaryotic cells can grow only when their membrane lipids are largely in the fluid state, i.e., at temperatures above the gel to liquid-crystalline transition temperature (T m) of their membrane lipids (see McElhaney, this volume). Adaptation of bacteria (Cronan, 1975; Fulco, this volume), yeast (Watson, this volume), fungi (Miller and Barran, this volume), higher plants (Mazliak, 1979), and the protozoan Tetrahymena (Thompson and Nozawa, this volume) to temperatures below their normal growth temperatures generally results in changes in membrane lipid composition leading to increases in fatty acid unsaturation. The major factor affecting the fluidity of membrane lipids in eukaryotes, apart from the presence of cholesterol, is the degree of unsaturation of their fatty acid chains. This holds also for prokaryotes but, in addition, other factors such as chain length and branching may be important.
KeywordsMembrane Fluidity Desaturase Activity Microsomal Membrane Polyenoic Fatty Acid Desaturase System
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