ATP-dependent activation of a new form of spinach leaf 6-phosphofructo-2-kinase/fructose2,6-bisphosphatase

Griffin H. Walker, Steven C. Huber

Research output: Contribution to journalArticle

Abstract

A novel form of 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase that possesses little 2-kinase or bisphosphatase activity as isolated has been partially purified from spinach (Spinacia oleracea L.) leaves. However, the new form can be activated by pretreatment with Mg · ATP at room temperature. After ATP activation, the fructose 2,6-bisphosphatase activity has a Michaelis constant for fructose 2,6-bisphosphate of about 1 mm, and is inhibited by high substrate concentrations (greater than 2 mm) and both end products. The kinase/phosphatase activity ratio of the new form was dependent on pH and varied from 0.3 at pH 7.0 to 5.0 at pH 8.2. In contrast, the previously characterized form of the enzyme (which is isolated in an active form and is unaffected by preincubation with Mg · ATP) had an activity ratio of about 2 that was insensitive to pH over the range tested. The ATP-dependent activation of the new enzyme form was stimulated by fructose 6-phosphate and inhibited by glucose 6-phosphate. These results explain why activation is not observed during assay of this enzyme, and indicate that the activation process may be regulated by metabolites. Collectively, these data provide further evidence for the existence, in spinach leaves, of two molecular forms of the enzyme which exhibit different kinetic properties.

Original languageEnglish (US)
Pages (from-to)58-64
Number of pages7
JournalArchives of Biochemistry and Biophysics
Volume258
Issue number1
DOIs
StatePublished - Oct 1987

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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