Ceruloplasmin as low-density lipoprotein oxidase: activation by ascorbate and dehydroascorbate.
The ability of ceruloplasmin (Cp) to oxidize low-density lipoproteins (LDL) in the presence of water-soluble antioxidants was investigated and a reaction mechanism proposed. Ascorbate strongly enhanced LDL oxidation, but only after its rapid consumption. Dehydroascorbate enhanced Cp-mediated LDL oxidation even more strongly. Lipid-soluble antioxidants and water-soluble peroxides did not show noticeable activation. However, loading of LDL with lipid hydroperoxides increased the initial oxidation rate. We conclude that Cp mediates a localized redox cycle, where reduction of Cp-Cu2+ is effected by water-soluble reductants and reoxidation by liposoluble hydroperoxides.
Feichtenhofer
S
S
Institute of Molecular Biology, Biochemistry and Microbiology, SFB Biomembrane Research Centre, University of Graz, Schubertstrasse 1, A-8010, Graz, Austria.
Fabjan
J S
JS
Abuja
P M
PM
D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology; D002570:Ceruloplasmin / Q000378:metabolism*; D003300:Copper / Q000378:metabolism; D003683:Dehydroascorbic Acid / Q000378:metabolism / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D008054:Lipid Peroxides / Q000378:metabolism / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction / Q000187:drug effects; D019163:Reducing Agents / Q000378:metabolism / Q000494:pharmacology; D012995:Solubility; D014810:Vitamin E / Q000378:metabolism; D014867:Water / Q000378:metabolism
D000975:Antioxidants; D008054:Lipid Peroxides; D008077:Lipoproteins, LDL; D019163:Reducing Agents; D014867:Water; D014810:Vitamin E; D003300:Copper; D002570:Ceruloplasmin; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid