REACTION OF N-(CARBOBENZYLOXY)-L-HISTIDINE WITH E-2-OCTENAL

We have investigated the reaction of N-(carbobenzyloxy)-L-histidine with E-2-octenal and analyzed the products to identify the components that produce a significant loss of histidine residues in the reaction of E-2-octenal and proteins. When the mixture of N-(carbobenzyloxy)-L-histidine and E-2-octenal was incubated at pH 7.0 and 37 degrees C for 24 h, E-2-octenoic acid and isomeric forms of N-(carbobenzyloxy)-1-(3)-(1'-(formylmethyl)hexyl)-L-histidine were obtained. Althought other possibilities are not excluded, it is suggested that the modification of histidine residues in proteins by E-2-octenal involves a Michael-type addition of the imidazole nitrogen atom of histidine to the alpha,beta-unsaturated bond of E-2-octenal.