title: Effect of salts on the solubility of thermolysin: a remarkable increase in the solubility as well as the activity by the addition of salts without aggregation or dispersion of thermolysin.
abstract: Thermolysin is remarkably activated in the presence of high concentrations (1-5 M) of neutral salts [Inouye, K. (1992) J. Biochem. 112, 335-340]. The activity is enhanced 13-15 times with 4 M NaCl at pH 7.0 and 25 degrees C. In this study, the effect of neutral salts on the solubility of thermolysin has been examined. Although the solubility was only 1.0-1.2 mg/ml in 40 mM Tris-HCl buffer, pH 7.5, in the temperature range between 0 and 60 degrees C, it was increased greatly by the addition of salts. With NaCl, the solubility showed a bell-shaped behavior with increasing NaCl concentration, and the maximum solubility (10 mg/ml) was at 2.0-2.5 M NaCl. With LiCl and NaI, it increased progressively to 20-50 mg/ml with increasing salt concentration up to 5 M. The solubility observed in the presence of salts decreased with increasing temperature from 0 to 60 degrees C, and also with the order of chaotropic anion effect. The molecular weight of thermolysin was estimated to be 33.0(+/-2.5) x 10(3) in the presence of 0-3 M NaCl, suggesting that thermolysin exists as a monomer in the presence or absence of 3 M NaCl. The possibility that aggregation and/or dispersion of thermolysin might be related to the remarkable activation by salt was ruled out.
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan. inouye@kais.kais.kyoto-u.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Inouye
authors.forename: K
authors.initials: K
authors.lastname: Kuzuya
authors.forename: B
authors.initials: B
authors.lastname: Tonomura
mesh_terms: D000179:Acrylates / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008970:Molecular Weight; D012492:Salts; D012995:Solubility; D013696:Temperature; D013820:Thermolysin / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D000179:Acrylates; D004151:Dipeptides; C108649:N-(3-(2-furyl)acryloyl)glycyl-leucinamide; D012492:Salts; D013820:Thermolysin