Sep 22, 1975

Studies of homogeneous "biosynthetic" L-threonine dehydratase from Escherichia coli K-12. Some kinetic properties and molecular multiplicity

Biochimica Et Biophysica Acta
Z S KaganL I Yakovleva

Abstract

"Biosynthetic" L-threonine dehydratase (EC 4.2.1.16) was purified to a homogeneous state with 29% yield of total activity from Escherichia coli K-12. The homogeneity of the enzyme was shown by polyacrylamide gel disc electrophoresis in the presence of dodecyl sulphate. The enzyme consisted of equal subunits having a molecular weight of about 57 000. The polyacrylamide gel disc electrophoresis has shown that the native enzyme consisted of a set of oligomeric forms. The multiplicity of molecular organization of the enzyme was reflected in complicated kinetic behaviour: at pH greater than 9 on the plots of initial reaction rate (v) versus initial substrate concentration ([S]o) there were four inflexion points (two intermediate plateaux), the position and deepness of which depended on enzyme concentration. At pH 8.3 on the v versus [S]o plots appeared two inflexion points (one intermediate plateu), the position of which practically did not depend on enzyme concentration in the reaction mixture, but strongly depended on the enzyme concentration in the stock solution. Repeated polyacrylamide gel disc electrophoresis of several oligomeric forms, isolated by the first electrophoresis, has shown that the oligomeric forms underwent a slo...Continue Reading

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Mentioned in this Paper

Macromolecular Compounds
Alkalescens-Dispar Group
Polyacrylamide Gels
Threonine Dehydratase
Lyase
Electrophoresis, Disc
Hydro-Lyases
Escherichia coli
Anabolism
KRT12

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