Haruo Kanazawa

Studies on the active site of papain. VII. States of tryptophan residues.

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.