title: Stopped-flow chemical modification with N-bromosuccinimide: a good probe for changes in the microenvironment of the Trp 62 residue of chicken egg white lysozyme.
abstract: The stopped-flow chemical modification with N-bromosuccinimide (NBS) of Trp 62 of hen (chicken) egg white lysozyme (EC 3.2.1.17) was found to depend greatly on pH: it was not observed at pH's above 7, but it was observed at pH's lower than 6. In addition, at pH's between 6 and 7 the NBS modification showed a delta epsilon pH profile similar to a "titration curve," giving a pK (congruent to 6.5) nearly equal to the pK (congruent to 6.2) of a catalytic residue, Glu 35. The stopped-flow chemical (NBS) modification of N-acetyl-L-tryptophan ethyl ester, a model compound of Trp 62, does not depend on pH at the pH's examined, approximately 3.5-8.5. These experimental results suggest that a change in the state of Trp 62 at Subsite C is induced by protonation-deprotonation of an ionizable residue, which could be Glu 35 (catalytic site), indicating that stopped-flow NBS modification is a good probe for detection of changes in the micorenvironment around the tryptophan residue(s) of enzymes.
authors.affiliation: Department of Food Science and Technology, College of Agriculture, University of Kyoto, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ohnishi
authors.forename: T
authors.initials: T
authors.lastname: Kawagishi
authors.forename: K
authors.initials: K
authors.lastname: Hiromi
mesh_terms: D001665:Binding Sites; D001974:Bromosuccinimide; D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009113:Muramidase / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship; D013388:Succinimides; D014364:Tryptophan
chemical_list: D013388:Succinimides; D014364:Tryptophan; D009113:Muramidase; D001974:Bromosuccinimide