V. Amamath et al., REACTIONS OF 4-HYDROXY-2(E)-NONENAL AND RELATED ALDEHYDES WITH PROTEINS STUDIED BY C-13 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY, Chemical research in toxicology, 11(4), 1998, pp. 317-328
In order to understand the modifications of proteins produced by aldeh
ydes of lipid peroxidation, [1-C-13]-2(E)-hexenal, [1-C-13]-4-oxopenta
nal, and a mixture of [1-C-13]- and [2-C-13]-4-hydroxynon-2(E)-enal we
re synthesized and the reaction of each of the labeled aldehydes with
bovine serum albumin was analyzed by C-13 NMR spectroscopy. Protein nu
cleophiles add to the 3-position of hexenal, and the resulting propana
l moieties appear to undergo aldol condensation, form imine cross-link
s with lysyl residues, or lead to pyridinium rings. During the reactio
n of 4-oxopentanal with the lysyl residues of bovine serum albumin, on
ly 1-alkyl-2-methylpyrrole and a possible intermediate leading to the
pyrrole were observed. Hydroxypyrrolidine cross-links such as 25 could
not be detected, leaving the pyrrole as the mediator of protein cross
-linking. The Michael adducts are the major products in the reaction b
etween 4-hydroxynon-2-enal and proteins. They exist almost exclusively
in the cyclic hemiacetal form and do not appear to cross-link through
imine formation with lysyl residues. A minor pathway involves the rea
ction of 4-hydroxynon-2-enal with the lysyl amino groups of protein re
sulting in 2-pentylpyrrole adducts that may mediate protein cross-link
ing. The Michael adducts appear not to be the direct source of the pyr
role, but the imine 32 and the enamine 35 are likely intermediates tow
ard the five-membered ring.