Changes induced in bovine serum albumin following interactions with the lipid peroxidation product E-2-octenal.

Bovine serum albumin (BSA) undergoes a number of deteriorative changes when exposed to E-2-octenal. Reaction of BSA with E-2-octenal produced fluorescent BSA with an excitation maximum at 350 nm and emission maximum at 440 nm and promoted polymerization. Amino acid analysis of the modified BSA showed that the E-2-octenal treatment leads to the selective loss of lysine residues and the formation of new amino acid derivatives. The same products were detected in acid hydrolysates of poly-L-lysine and N2-(carbobenzyloxy)-L-lysine after their reactions with E-2-octenal. The reaction of N2-(carbobenzyloxy)-L-lysine with E-2-octenal led to the production of 1-[N2-(carbobenzyloxy)-L-lysyl]-2- (1'-carboxymethyl)-4-pentylpyridinium betaine, 1-[N2-(carbobenzyloxy)-L-lysyl]-2- (3'-carboxy-2'-E-propen-1'-yl)-4- pentylpyridinium betaine and bis[1-[N2-(carbobenzyloxy)-L-lysyl]-2- (3'-carboxy-2'-propen-1',2'-diyl)- 4-pentylpyridinium betaine] (isomeric mixture). Upon acid hydrolysis, these quaternary pyridinium salts led to new amino acid derivatives, presumably 1-(L-lysyl)-2-(1'-carboxymethyl)-4-pentylpyridinium betaine, 1-(L-lysyl)-2-(3'-carboxy-2'-E-propen-1'-yl)- 4-pentylpyridinium betaine and bis[1-(L-lysyl)-2-(3'-carboxy-2'-propen-1',2'-diyl)- 4-pentylpyridinium betaine] (isomeric mixture) that were indistinguishable from those obtained from BSA, poly-L-lysine and N2-(carbobenzyloxy)-L-lysine after similar treatment. The reaction of lysine residues with E-2-octenal provides the basis for methods by which the contributions of E-2-octenal in the modifications of proteins can be determined.