Schematic representation CEP and EP formation. PLA₂-catalyzed hydrolysis of DHA generates HOHA, which, in turn, produces CEP–protein derivatives through condensation with the primary amino groups of protein lysyl residues, as was described previously.¹⁸  A structurally similar protein modification, EP, is generated through the alternative oxidative cleavage of DHA to give 4-hydroxyhex-2-enal followed by condensation of 4-hydroxyhex-2-enal with the ε-amino group of lysyl residues. Compared with CEP, this modification lacks a carboxyl group. HHE, 4-hydroxyhexenal; HOHA, 4-hydroxy-7-oxo-hept-5-eonate.