Reversible inactivation of avian lysozymes by dimethyl (2-hydroxy-5-nitrobenzyl)-sulfonium bromide

The reaction of hen egg white lysozyme with a 4 molar excess of dimethyl (2-hydroxy-5-nitrobenzyl)-sulfonium bromide at pH 6.0 leads to total loss of enzymatic activity within 5 minutes. Upon standing, the inactivated enzyme spontaneously regains activity, leveling off at 60% of the original activity after 72 hours. Under the same conditions, turkey egg white lysozyme is reduced to less than 5% of its original activity within 5 minutes, then spontaneously reactivates to 85% of its original activity after 24 hours. Human lysozyme shows no dramatic loss of activity when treated under these conditions. The presence of the substrate, chitotetraose, prevents the initial inactivation of both hen and turkey enzymes.