A novel mechanism involved in the metabolism of the tartaric acid stereoisomers in Rhodopseudomonas sphaeroides: enzymatic conversion of meso-tartaric acid to D(-)-glyceric acid and CO2 |
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Authors: | Holger Ebbighausen Friedrich Giffhorn |
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Institution: | (1) Institut für Mikrobiologie der Universität Göttingen, Grisebachstraße 8, D-3400 Göttingen, Germany |
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Abstract: | In cell extracts of Rhodopseudomonas sphaeroides grown on meso-tartrate the activities of the bifunctional L(+)-tartrate dehydrogenase-D(+)-malate dehydrogenase (decarboxylating) (EC 1.1.1.93 and 1.1.1.83, respectively) could be measured spectrophotometrically but not the activity of a meso-tartrate dehydrogenase or dehydratase. However, an enzyme activity was detected manometrically that catalyzed the stoichiometric release of CO2 from mesotartrate in a molar ratio of 1:1. This reaction required catalytic amounts of NAD and the presence of both divalent (Mn2+ or Mg2+) and monovalent (NH
4
+
or K+) cations. Purification of the meso-tartrate decarboxylase showed that it was part of the bifunctional L(+)-tartrate dehydrogenase-D(+)-malate dehydrogenase (decarboxylating), which thus possessed a third catalytic function. The homogeneous enzyme catalyzed the stoichiometric conversion of incso-tartaric acid to D(-)-glyceric acid and CO2. All interfering catalytic activities had been eliminated during the course of enzyme purification. |
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Keywords: | L(+)-Tartrate dehydrogenase" target="_blank">L(+)-Tartrate dehydrogenase Multifuctional enzyme Meso-tartrate conversion D(-)-glyceric acid" target="_blank">Formation of D(-)-glyceric acid |
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