Stability-increasing mutants of glucose dehydrogenase

Abstract

Four stability-increasing mutants of glucose dehydrogenase from Bacillus megateriun were purified together with the wild-type enzyme; each has a single amino acid change of Glu-96 to Gly, Glu-96 to Ala, Gln-252 to Leu, or Tyr-253 to Cys. These mutant enzymes are more heat resistant at pH 6.5 than the wild-type enzyme; the replacement of Glu-96 by Ala increases the thermostability by about 20°C. The mutant enzymes are also resistant to inactivation in alkaline solutions. The replacement of Glu-96 by Gly or Ala protects the enzyme from alkaline inactivation almost completely. The kinetic constants for the activities of these mutant enzymes do not differ significantly from those of the wild-type enzyme. © 1989.