Dissociation of β-Galactosidase by Thiols

Abstract

IT is common practice to add mercaptoethanol to solutions of β-galactosidase during purification from Escherichia coli and to the stock solutions of the enzyme during storage. Although Craven et al.¹ had reported that mercaptoethanol stabilizes the enzyme isolated from the K12 strain against thermal inactivation, Reithel and his coworkers² observed that the enzyme from strain ML308 is readily inactivated in the presence of thiols. In previous studies from this laboratory³ we used the buffer system first reported by Craven et al.¹ which consists of 0.05 M Tris-HCl, 0.01 M MgCl₂, 0.10 M NaCl and 0.05 M β-mercaptoethanol (pH 7.5).