Identification of tryptophan 62 as an ozonization-sensitive residue in hen egg-white lysozyme

The position of a single N'-formylkynurenine residue in ozone-inactivated hen egg-white lysozyme [EC 3.2.1.17] was determined by two methods. One involved identification of an amino-terminus of the C-peptide obtained by selective cleavage with hydrazine of the kynurenyl peptide linkage in oxidized lysozyme. The other was to analyze a tryptic peptide containing kynurenine in the modified enzyme. Both methods showed that tryptophan 62 in lysozyme was so sensitive to ozone as to be selectively oxidized to N'-formylkynurenine with concomitant loss of the lytic activity.