Dissociation of mitochondrial malate dehydrogenase

J. Muller, H. Gorisch, L. J. Parkhurst

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The kinetics of the dissociation reaction under acidic conditions of the dimeric pig and chicken mitochondrial malate dehydrogenases (EC have been studied. The dissociation of the pig enzyme is completely reversible. The pK for dissociation determined by light-scattering measurements agrees within experimental error with the pK value of 5.25 measured for a tyrosine-carboxylate pair. The rate constants for the dissociation reaction and for the protonation process of this tyrosine are in close agreement. Thus, the tyrosine-carboxylate pair can be used as indicator of the dissociation reaction. The dissociation of the chicken enzyme proceeds around pH 4.5 at a much lower rate. A true equilibrium between dimer and monomers is not found, since the monomer gradually unfolds at this pH. The monomers of both enzymes, pig and chicken mitochondrial malate dehydrogenase, show the same stability towards acid. The difference in stability of the dimeric forms, therefore, must be due to an altered subunit contact area.

Original languageEnglish (US)
Pages (from-to)258-263
Number of pages6
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Issue number3
StatePublished - Jun 28 1984
Externally publishedYes


  • Acid dissociation
  • Malate dehydrogenase
  • Tyrosine (Mitochondria)

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology


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