Mechanism, hydroperoxides imines

Reaction products of reactive aldehydes derived from oxidised lipids, such as acrolein, ( )-4-hydroxynon-2-enal and malondi-aldehyde, with lysine, arginine and other amino acids are described as examples in Section 4.7.5.6. These products, ALE (advanced lipoxidation end products), formed in vivo are markers of oxidative stress in the organism. Reaction mechanisms are discussed in Section 3.8.1.12.1. As the final reaction products, proteins and oxidised lipids also form dark insoluble macromolecular products that contain variable proportions of lipid and protein fractions. In particular, such products include protein oligomers, proteins with oxidised sulfur amino acids, proteins containing imine bonds (C=N) formed by reaction with aldehydes or hydroperoxides (they mostly arise from the -amino group of bound lysine) and... 

Figure 7.19 The mechanism of N-oxidation relies on a flavin moiety of MFO undergoing reduction by NADPH.The intermediate formed reacts with molecular oxygen to form a hydroperoxide. The terminal oxygen of a hydroperoxide is electrophilic and can react with nucleophiles such as the lone pair of an imine leading to imine oxide formation. The flavin unit undergoes a ring-opening and ring-closure sequence and finally eliminates water to give back the oxidized flavin unit that can continue in the catalytic cycle. Based on Figure 13 in reference [3].

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