title: Effects of salts on the interaction of 8-anilinonaphthalene 1-sulphonate and thermolysin.
abstract: Neutral salts activate and stabilize thermolysin. In this study, to explore the mechanism, we analyzed the interaction of 8-anilinonaphthalene 1-sulphonate (ANS) and thermolysin by ANS fluorescence. At pH 7.5, the fluorescence of ANS increased and blue-shifted with increasing concentrations (0-2.0 μM) of thermolysin, indicating that the anilinonaphthalene group of ANS binds with thermolysin through hydrophobic interaction. ANS did not alter thermolysin activity. The dissociation constants (Kd) of the complex between ANS and thermolysin was 33 ± 2 μM at 0 M NaCl at pH 7.5, decreased with increasing NaCl concentrations, and reached 9 ± 3 μM at 4 M NaCl. The Kd values were not varied (31-34 μM) in a pH range of 5.5-8.5. This suggests that at high NaCl concentrations, Na(+) and/or Cl(-) ions bind with thermolysin and affect the binding of ANS with thermolysin. Our results also suggest that the activation and stabilization of thermolysin by NaCl are partially brought about by the binding of Na(+) and/or Cl(-) ions with thermolysin.
authors.affiliation: a Division of Food Science and Biotechnology, Graduate School of Agriculture , Kyoto University , Sakyo-ku , Japan.
authors.forename: Vimbai
authors.initials: V
authors.lastname: Samukange
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kamo
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Yasukawa
authors.forename: Kuniyo
authors.initials: K
authors.lastname: Inouye
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D004151:Dipeptides; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D012965:Sodium Chloride / Q000737:chemistry*; D013820:Thermolysin / Q000737:chemistry* / Q000378:metabolism
chemical_list: C515594:8-anilino-1-naphthalenesulfonic acid; D000817:Anilino Naphthalenesulfonates; D004151:Dipeptides; D012965:Sodium Chloride; D013820:Thermolysin
keywords: ANS; metalloproteinase; salt-induced activation; salt-induced stabilization; thermolysin