Regulation of succinate dehydrogenase and tautomerization of oxaloacetate

Andrei D. Vinogradov, Alexander B. Kotlyar, Victor I. Burov, Yuliya O. Belikova

Research output: Contribution to journalArticlepeer-review

Abstract

Highly purified succinate-ubiquinone reductase catalyzes the oxidation of l- or d-malate with a Km and initial Vmax equal to ∼ 10-3 m and ∼ 100 nmol/min/mg of protein, respectively. The malate dehydrogenase activity of succinate dehydrogenase rapidly decreases regardless of the presence of glutamate plus glutamate-oxaloacetate transaminase. The inhibitor trapping system, however, prevents the inactivation of succinate dehydrogenase under the conditions when the rate of tautomeric oxaloacetate enol ↔ oxaloacetate ketone interconversion is high. These results suggest that enol oxaloacetate is an immediate product of malate oxidation at the succinate dehydrogenase active site. Two proteins (Mr 37 and 80 kD) which catalyze the oxaloacetate tautomerase reaction were isolated from the mitochondrial matrix. Some physico-chemical and kinetic properties of these enzymes were characterized. The larger protein was identified as inactive aconitase. The system containing succinate dehydrogenase, l-malate, glutamate plus transaminase and oxaloacetate tautomerase was reconstituted. Such a system is capable of oxidizing malate to aspartate without rapid inactivation of succinate dehydrogenase. Taken together, the data obtained emphasize a significant role of enzymatic oxaloacetate tautomerization in the control of the succinate dehydrogenase activity in the mitochondrial matrix.

Original languageEnglish
Pages (from-to)271-280
Number of pages10
JournalAdvances in Enzyme Regulation
Volume28
Issue numberC
DOIs
StatePublished - 1989

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