Chorismate Mutase-Prephenate Dehydratase from Escherichia coli K-12

Abstract

Abstract A single protein that catalyzes both the rearrangement of chorismate to prephenate and the dehydration of prephenate to phenylpyruvate has been purified from an operator-constitutive mutant strain of Escherichia coli K-12. The enzyme appeared to be homogeneous on acrylamide gel electrophoresis of oxidized material in 8 m urea. The ratio of mutase to dehydratase activities remained essentially constant throughout the purification. Gel filtration of the enzyme on Sephadex G-100 indicated the presence of two active species. The molecular weight of the major species was approximately 85,000 and that of the minor species (approximately 10% of the total) was approximately 137,000. A value of approximately 40,000 for the minimum molecular weight was obtained from acrylamide gel electrophoresis of performic acid-oxidized enzyme in 8 m urea. It is proposed that the native enzyme exists in solution mainly as a dimer of similar and possibly identical subunits. The amino acid composition of the enzyme is reported.