Oxidation of Cholesterol Catalyzed by Amyloid β-Peptide (Aβ)-Cu Complex on Lipid Membrane(ENZYMOLOGY, PROTEIN ENGINEERING, AND ENZYME TECHNOLOGY)

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A catalytic reaction of H_2O_2 production by an amyloid β-peptide (Aβ)-Cu complex with cholesterol incorporated in a liposome was kinetically analyzed. The Michaelis-Menten model was applied to the H_2O_2 production reaction using cholesterol as the substrate catalyzed by the Aβ-Cu complex. The K_m value for the Aβ-Cu complex catalytic reaction with cholesterol-containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) liposomes (K_m=0.436μM for Aβ(1-40); K_m=0.641μM for Aβ(1-42)) was found to be smaller than that with cholesterol-containing 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes (K_m=0.585μM for Aβ(1-40), K_m=0.890μM for Aβ(1-42)). The results imply that membrane properties could play an important role in the interactions of the Aβ-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 H_2O_2-generating activity of the Aβ-Cu complex, accompanied by oxidation of membrane-incorporated cholesterol, could be effected by the phase of the liposome membranes.
公益社団法人日本生物工学会の論文
2005-10-25