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The substrate specificity, kinetics, and mechanism of glycerate-3-kinase from spinach leaves

Authors
Journal
Archives of Biochemistry and Biophysics
0003-9861
Publisher
Elsevier
Publication Date
Volume
236
Issue
1
Identifiers
DOI: 10.1016/0003-9861(85)90618-6
Keywords
  • Plant Biochemistry And Photosynthesis
Disciplines
  • Biology

Abstract

Abstract Glycerate-3-kinase (EC 2.7.1.31) from spinach leaves shows absolute specificity for d-glycerate as phosphate acceptor, yielding 3-phosphoglycerate as a product. ATP complexed with either Mg 2+ or Mn 2+ is the preferred phosphate donor. The enzyme has K m (D-glycerate) = 0.25 mM, K m (Mg-ATP) = 0.21 mM, V max = 300 μmol min −1 mg protein −1, and a turnover number = 12,000·min −1. The equilibrium constant for the reaction is approximately 300 at pH 7.8. Pyrophosphate, 3-phosphoglycerate and ribulose 1,5-bisphosphate are the strongest inhibitors among the phosphorylated and nonphosphorylated metabolites tested; however, their regulatory role in vivo is questioned. Substrate kinetics, as well as product and analog inhibition data, are consistent with a sequential random mechanism. The distinct characteristic of the glycerate kinase-catalyzed reaction is the formation of a dead-end complex between the enzyme, d-glycerate, and 3-phosphoglycerate.

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