ABSTRACT
Preparations of intrinsic membrane-enzymes solubilized by detergent and purified by ammonium sulfate fractionation or column chromatography in the presence of detergent usually contain protein-associated lipid. There have been several general reviews on the lipid dependence of membrane enzymes, and specific aspects of the subject have also been covered including prokaryote membrane-bound enzymes, protein-lipid interactions, topology and reconstitution, and lipid effects on various transport and receptor systems. Isolation of membrane-associated glycoprotein and its subsequent purification can be achieved from the upper aqueous layer, organic solvent procedures are not suited to reversible delipidation of amphipatic proteins. In many membranes, lipid is covalently bound to membrane protein and full delipidation by detergent or solvent treatment is not possible. Changes in diet or growth conditions can cause changes in the fatty acid composition of membrane lipids, and these often affect the activity of membrane-associated enzymes.
