This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (26) Citing Articles via Google Scholar Google Scholar Articles by Miernyk, J. A. Articles by Randall, D. D. Search for Related Content PubMed PubMed Citation Articles by Miernyk, J. A. Articles by Randall, D. D. Agricola Articles by Miernyk, J. A. Articles by Randall, D. D.

Metabolism and Enzymology

Some Kinetic and Regulatory Properties of the Pea Mitochondrial Pyruvate Dehydrogenase Complex ¹

Biochemistry Department, 322A Chemistry Building, University of Missouri, Columbia, Missouri 65211

The pyruvate dehydrogenase complex was isolated, partially purified, and characterized from green pea (Pisum sativum L., cv Little Marvel) leaf mitochondria. The pH optimum for the overall reaction was 7.6. The divalent cation requirement was best satisfied by Mg²⁺. Reaction velocity was maximal at 40°C. Pyruvate was a better substrate than 2-oxo-butyrate; other 2-oxo-acids were not substrates. Michaelis constants for substrates were; pyruvate, 57 micromolar; NAD, 122 micromolar; Coenzyme-A, 5 micromolar; Mg²⁺, 0.36 millimolar; Mg-thiamine pyrophosphate, 80 nanomolar. The products, NADH and acetyl-Coenzyme-A, were linear competitive inhibitors with respect to NAD and Coenzyme A. Inhibition constants were 18 and 10 micromolar, respectively. Glyoxylate inhibited complex activity only in the absence of thiol reagents. Glyoxylate inhibition was competitive with respect to pyruvate with an inhibition constant of 51 micromolar. Among mitochondrial metabolites examined as potential effectors, only ADP with an inhibition constant of 0.57 millimolar could be of physiological significance.

¹ Supported by National Science Foundation Grant PCM-8104569, and a fellowship to J. A. Miernyk from Monsanto. This is journal report 10,001 from the Missouri State Agricultural Experiment Station.

This article has been cited by other articles:

				J. J. Thelen, J. A. Miernyk, and D. D. Randall Partial Purification and Characterization of the Maize Mitochondrial Pyruvate Dehydrogenase Complex Plant Physiology, April 1, 1998; 116(4): 1443 - 1450. [Abstract] [Full Text]