Apolipoprotein E, the most common apolipoprotein found in the brain, is linked to several pathologies like Alzheimer's disease. Apolipoprotein E directly binds to beta-amyloid with a strong affinity. Myeloperoxidase, a protein secreted by neutrophils and involved in the inflammatory process, is also present in the brain. In vitro myeloperoxidase oxidation of recombinant human apolipoprotein E leads to fragmentation of the protein with low concentrations of hydrogen peroxide and polymerization with higher concentrations. Comparison with bovine serum albumin shows a higher susceptibility of apolipoprotein E to myeloperoxidase oxidation, which may have importance in the Alzheimer's disease process.