title: Carnosine is a quencher of 4-hydroxy-nonenal: through what mechanism of reaction?
abstract: The aim of this study was to understand the mechanism of action through which carnosine (beta-alanyl-L-histidine) acts as a quencher of cytotoxic alpha,beta-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 beta-alanine was totally inactive; this indicates that the two constitutive amino acids act synergistically when incorporated as a dipeptide and that the beta-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 alpha,beta-unsaturated imine, followed by ring closure through an intra-molecular Michael addition. The biological role of carnosine as a quencher of alpha,beta-unsaturated aldehydes was verified by detecting carnosine-HNE reaction adducts in oxidized rat skeletal muscle homogenate.
authors.affiliation: Istituto Chimico Farmaceutico Tossicologico, University of Milan, Viale Abruzzi 42, 20131 Milan, Italy. giancarlo.aldini@unimi.it
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Aldini
authors.forename: Marina
authors.initials: M
authors.lastname: Carini
authors.forename: Giangiacomo
authors.initials: G
authors.lastname: Beretta
authors.forename: Silvia
authors.initials: S
authors.lastname: Bradamante
authors.forename: Roberto Maffei
authors.initials: RM
authors.lastname: Facino
mesh_terms: D000447:Aldehydes / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002336:Carnosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D066298:In Vitro Techniques; D015227:Lipid Peroxidation; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
chemical_list: D000447:Aldehydes; D017392:Thiobarbituric Acid Reactive Substances; C033681:N-acetylcarnosine; D002336:Carnosine; C027576:4-hydroxy-2-nonenal