title: 5'-Nucleotidase is activated upon cholesterol-depletion of liver plasma membranes.
abstract: The cholesterol content of rat liver plasma membranes was manipulated using either cholesterol-free or cholesterol-enriched liposomes. Removal of cholesterol from the membranes led to a marked increase in 5'-nucleotidase activity. However, increase in cholesterol content failed to exert any significant effect on 5'-nucleotidase activity. Arrhenius plots of the activity of the native enzyme exhibited a break at around 28 degrees C with the activation energy of the reaction less above this temperature than below. In cholesterol-depleted membranes a single break at around 26 degrees C was observed with activation energies greater above this temperature than below it. In cholesterol-enriched membranes Arrhenius plots were linear over the range examined. It is suggested that the lipid environment of the external half of the bilayer only influences 5'-nucleotidase activity in these membranes and that cholesterol exerts controlling effects on both the activity and conformation of the enzyme in native membranes.
mesh_terms: D015720:5'-Nucleotidase; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D002784:Cholesterol / Q000378:metabolism*; D004789:Enzyme Activation; D066298:In Vitro Techniques; D008081:Liposomes; D008099:Liver / Q000201:enzymology*; D008297:Male; D009708:Nucleotidases / Q000378:metabolism*; D011663:Pulmonary Surfactants; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D008081:Liposomes; D011663:Pulmonary Surfactants; D002784:Cholesterol; D009708:Nucleotidases; D015720:5'-Nucleotidase