The activation of ox-brain NAD [nicotinamide adenine dinucleotide] (+)-dependent isocitrate dehydrogenase by magnesium ions

Two independent methods were used to assess the dependence of the activity of ox brain NAD+‐dependent isocitrate dehydrogenase on the concentration of magnesium ions. The results indicated the complex between magnesium and isocitrate to be the true substrate for the enzyme. Free isocitrate is neithe...

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Bibliographic Details
Published in:	European journal of biochemistry Vol. 113; no. 3; pp. 477 - 483
Main Authors:	Willson, V.J.C, Tipton, K.F. (Cambridge Univ. (UK). Dept. of Biochemistry)
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Publishing Ltd 1981
Subjects:	Adenosine Diphosphate - pharmacology Adenosine Triphosphate - pharmacology Animals Brain - enzymology Cattle Citrates - pharmacology Enzyme Activation - drug effects In Vitro Techniques Isocitrate Dehydrogenase - antagonists & inhibitors Isocitrate Dehydrogenase - metabolism Magnesium - pharmacology Male NAD - pharmacology Substrate Specificity
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Summary:	Two independent methods were used to assess the dependence of the activity of ox brain NAD+‐dependent isocitrate dehydrogenase on the concentration of magnesium ions. The results indicated the complex between magnesium and isocitrate to be the true substrate for the enzyme. Free isocitrate is neither a substrate nor an inhibitor of the enzyme but free magnesium ions inhibit competitively with respect to the magnesium‐isocitrate complex. The inhibition of the enzyme by ATP and citrate appears to be largely explicable in terms of their effects on the concentration of the complex between Mg2+ and isocitrate. The dependence of the activation of the enzyme by ADP on the concentration of magnesium ions suggests that free ADP, rather than its, complex with Mg2+, is the activator.
Bibliography:	814X242 L50 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0014-2956 1432-1033
DOI:	10.1111/j.1432-1033.1981.tb05088.x