Alzheimer disease β-amyloid activity mimics cholesterol oxidase
J. Clin. Invest. Luigi Puglielli, et al. 115:2556 doi:10.1172/JCI23610 [Go to this article.]

Figure 1
Cholesterol oxidase activity of Aβ:Cu²⁺. (A) Chemical structure of cholesterol showing oxidation of the hydroxyl group at position C-3 by cholesterol oxidase activity. (B and C) The migrations of nonoxidized cholesterol and 4-cholesten-3-one standards are shown. (B) Oxidation of cholesterol (50 μM) after incubation with BSA/Cu²⁺ (1 μM:2 μM), Aβ₄₂ (1 μM), Cu²⁺ (2 μM), Aβ₄₂:Cu²⁺ complex (1 μM:2 μM), or bacterial cholesterol oxidase (BCO; 5 IU). (C) Effect of Cu²⁺ chelation (with 1 mM TETA) on 4-cholesten-3-one generation by the Aβ₄₂:Cu²⁺ complex; conditions as in B. Data are representative of at least 3 experiments. (D) Generation of 4-cholesten-3-one on TLC of Aβ₄₀ and Aβ₄₂ complexed with Cu²⁺ (1 μM:2 μM), and inhibition by the Cu²⁺ chelator CQ (100 μM). Bars show mean ± SD. Significance was calculated by 2-tailed Student’s t test of CQ effect. *P < 0.05. RU, relative units. (E) Total ion current mass chromatograms obtained by repetitive scanning GC-MS analysis of the underivatized compound and methyloxime derivative of the sample eluted from the TLC spot were superimposed for comparison with pure standard of 4-cholesten-3-one. The retention indices of each compound are denoted in MU. (F) Electron ionization (70 electron volts) mass spectrum of a compound identified as 4-cholesten-3-one by TLC from extracts of AD brain tissue eluted from the TLC plate: underivatized compound (top), 4-cholesten-3-one standard (middle), methyloxime derivative of the TLC extract (bottom; syn-isomer only shown) confirming the expected shift in masses of the molecular and fragment ions.