title: S-adenosyl-L-methionine modulates Na+ + K+-ATPase activity in rat colonic basolateral membranes.
abstract: Rat colonic basolateral membranes were incubated with S-adenosyl-L-[methyl-3H]methionine (0.3 mM) at 37 degrees C for 2 h at pH 9.0. This resulted in an increase in the specific activity of Na+ + K+-ATPase by 60%. Kinetic parameter analysis revealed a 2-fold increase in the Vmax. of this enzymatic activity, whereas the Km for ATP was unchanged. The methylation inhibitor S-adenosyl-L-homocysteine (2 mM) significantly reduced these S-adenosyl-L-methionine-stimulated increases in specific activity and the Vmax. of Na+ + K+-ATPase. S-Adenosyl-L-methionine treatment of basolateral membranes was also found to significantly increase the fluidity of these preparations, as assessed by steady-state fluorescence polarization techniques using the fluorophore 1,6-diphenyl-1,3,5-hexatriene; S-adenosyl-L-homocysteine (2 mM) again markedly reduced this S-adenosyl-L-methionine-induced increase in fluidity. While transmethylation reactions involving phospholipids, non-polar lipids and proteins were all found to exist in rat colonic basolateral membranes, based on a number of observations, the results of the present studies suggest that transmethylation of membrane phospholipids, but not membrane non-polar lipids or proteins, influenced the fluidity of basolateral membranes which, in turn, modified Na+ + K+-ATPase activity in these membranes.
authors.affiliation: Department of Medicine, Michael Reese Hospital and Medical Center, Chicago, IL 60637.
authors.forename: M D
authors.initials: MD
authors.lastname: Brown
authors.forename: P K
authors.initials: PK
authors.lastname: Dudeja
authors.forename: T A
authors.initials: TA
authors.lastname: Brasitus
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000187:drug effects / Q000378:metabolism; D019905:Benzyl Alcohol; D001592:Benzyl Alcohols / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000201:enzymology*; D005454:Fluorescence Polarization; D007700:Kinetics; D050356:Lipid Metabolism; D008081:Liposomes / Q000378:metabolism; D008297:Male; D000432:Methanol / Q000494:pharmacology; D008745:Methylation; D010743:Phospholipids / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D012436:S-Adenosylmethionine / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D001592:Benzyl Alcohols; D008081:Liposomes; D010743:Phospholipids; D011506:Proteins; D012436:S-Adenosylmethionine; D000254:Sodium-Potassium-Exchanging ATPase; D019905:Benzyl Alcohol; D000432:Methanol