Carnosine is a quencher of 4-hydroxy-nonenal: through what mechanism of reaction?

• Published in: Biochemical and biophysical research communications Vol. 298; no. 5; pp. 699 - 706
• Main Authors: Aldini, Giancarlo, Carini, Marina, Beretta, Giangiacomo, Bradamante, Silvia, Facino, Roberto Maffei
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.11.2002
• Subjects: 4-Hydroxy- trans-2,3-nonenal; Aldehydes - chemistry; Aldehydes - metabolism; Animals; Carnosine; Carnosine - analogs & derivatives; Carnosine - chemistry; Carnosine - metabolism; ESI-MS; In Vitro Techniques; Lipid Peroxidation; Magnetic Resonance Spectroscopy; Male; Mass Spectrometry; Michael and imine adducts; Models, Biological; Muscle, Skeletal - metabolism; NMR; Oxidation-Reduction; Rat skeletal muscle; Rats; Rats, Wistar; Thiobarbituric Acid Reactive Substances - metabolism; ESI-MS; NMR; Carnosine; 4-Hydroxy- trans-2,3-nonenal; Michael and imine adducts; Rat skeletal muscle
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/S0006-291X(02)02545-7

The aim of this study was to understand the mechanism of action through which carnosine (β-alanyl- l-histidine) acts as a quencher of cytotoxic α,β-unsaturated aldehydes, using 4-hydroxy- trans-2,3-nonenal (HNE) as a model aldehyde. In phosphate buffer solution (pH 7.4), carnosine was 10 times more active as an HNE quencher than l-histidine and N-acetyl-carnosine while β-alanine was totally inactive; this indicates that the two constitutive amino acids act synergistically when incorporated as a dipeptide and that tshe β-alanyl residue catalyzes the addition reaction of the histidine moiety to HNE. Two reaction products of carnosine were identified, in a pH-dependent equilibrium: (a) the Michael adduct, stabilized as a 5-member cyclic hemi-acetal and (b) an imine macrocyclic derivative. The adduction chemistry of carnosine to HNE thus appears to start with the formation of a reversible α,β-unsaturated imine, followed by ring closure through an intra-molecular Michael addition. The biological role of carnosine as a quencher of α,β-unsaturated aldehydes was verified by detecting carnosine-HNE reaction adducts in oxidized rat skeletal muscle homogenate.