Substrate-dependent dissociation of malate thiokinase.

M. Elwell, L. B. Hersh

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Malate thiokinase has been purified to apparent homogeneity by employing conventional purification techniques along with affinity chromatography. The enzyme is composed of two nonidentical subunits (alpha subunit Mr=34,000, beta subunit Mr=42,500) to yield an alpha 4 beta 4 structure for the native enzyme. Phosphorylation of the enzyme by ATP occurs exclusively on the alpha subunit. The phosphorylated enzyme is acid labile and base stable consistent with phosphorylation of a histidine residue. Dephosphorylation of the enzyme is promoted by ADP, succinate, malate, and coenzyme A plus inorganic phosphate. Phosphorylation of the enzyme leads to a reversible change in the sedimentation properties of the enzyme; the native enzyme exhibits an S20,w of approximately 10, whereas the phosphoenzyme exhibits an S20,w of approximately 7. Formation of the 7 S form of the enzyme is also observed when coenzyme A and succinyl-CoA interact with the enzyme. The ratio of alpha to beta subunits in both the 10 S and 7 S forms of the enzyme is approximately 1.0, suggesting that the 7 S form of the enzyme has an alpha 2 beta 2 structure.

Original languageEnglish
Pages (from-to)2434-2438
Number of pages5
JournalJournal of Biological Chemistry
Issue number7
StatePublished - Apr 10 1979

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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