Abstract
1) The present research has been planed to clarify the states of tryptophan residues in papain by means of N-bromosuccinimide (NBS) oxidation and photooxidation. 2) Only a tryptophan residue was exclusively modified by NBS oxidation with the loss of enzyme activity. 3) This residue was not affected by methylene blue-sensitized photooxidation. 4) Two of five tryptophan residues were not affected by NBS oxidation and photooxidation. 5) The first NBS-oxidizable tryptophan residue is considered to exist in or nearby the active site of papain. 6) The second and the third NBS-oxidizable tryptophan residues are considered to be identical with the photooxidizable residues. 7) The state of tryptophan residues of papain was illustrated schematically.
