title: Oxidation of cholesterol catalyzed by amyloid beta-peptide (Abeta)-Cu complex on lipid membrane.
abstract: A catalytic reaction of H2O2 production by an amyloid beta-peptide (Abeta)-Cu complex with cholesterol incorporated in a liposome was kinetically analyzed. The Michaelis-Menten model was applied to the H2O2 production reaction using cholesterol as the substrate catalyzed by the Abeta-Cu complex. The Km value for the Abeta-Cu complex catalytic reaction with cholesterol-containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) liposomes (Km=0.436 microM for Abeta(1-40); Km=0.641 microM for Abeta(1-42)) was found to be smaller than that with cholesterol-containing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes (Km=0.585 microM for Abeta(1-40), Km=0.890 microM for Abeta(1-42)). The results imply that membrane properties could play an important role in the interactions of the Abeta-Cu complex with cholesterol in these liposomes. Considering the physical states of the cholesterol/POPC (liquid disordered phase) and cholesterol/DPPC (liquid ordered phase) liposomes in the present reaction conditions, the data obtained suggests that the H2O2-generating activity of the Abeta-Cu complex, accompanied by oxidation of membrane-incorporated cholesterol, could be effected by the phase of the liposome membranes.
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Yoshimoto
authors.forename: Makoto
authors.initials: M
authors.lastname: Tasaki
authors.forename: Toshinori
authors.initials: T
authors.lastname: Shimanouchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Umakoshi
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Kuboi
mesh_terms: D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D002384:Catalysis; D002784:Cholesterol / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000737:chemistry; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry*
chemical_list: D016229:Amyloid beta-Peptides; D008081:Liposomes; D008563:Membrane Lipids; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D003300:Copper; D002784:Cholesterol; D006861:Hydrogen Peroxide