Plant Physiol.
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Plant Physiology 77:346-351 (1985)
© 1985 American Society of Plant Biologists

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Articles

Kinetic Analysis of Corn Mitochondrial F1-ATPase 1

Bruce Partridge, Vitaly L. Spitsberg, Nancy E. Pfeiffer2 and Sheldon M. Schuster2

Department of Chemistry, and School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588-0304, Plant Breeding and Biometry, Cornell University, Ithaca, New York

The activation and catalytic mechanism of corn mitochondrial F1 were examined for the two distinct forms of the enzyme which appear upon storage in ammonium sulfate or glycerol. Apparently irreversible differences in the stability of the two active forms were found. Nucleosidetriphosphate induced activation of the enzyme was found to produce lasting effects on subsequent catalysis. These effects varied with both the nucleotide used for activation, and the hydrolyzed species. The substrate and metal specificity were examined with the ATP activated enzyme. Mg2+ and Ca2+ were found to be the most effective at promoting ATP hydrolysis. The substrates were hydrolyzed in the order GTP > ITP > ATP regardless of which nucleotide was used for activation. While ATP and GTP hydrolysis exhibited kinetics typical of other ATPases, ITP showed a transition from negative to positive cooperativity at low substrate concentrations. Bicarbonate was found to affect primarily the kinetics of ATP hydrolysis. AMP-PNP proved to be a potent inhibitor with respect to ATP hydrolysis. The results are discussed in terms of possible catalytic mechanisms and the similarities of the corn mitochondrial F1 to other ATPases.

2 Supported by National Institutes of Health Research service award CA 07420 from the National Cancer Institute, and Research Career Development Award CA00628 from the National Cancer Institute, Department of Health and Human Services (N. E. P., S. M. S.).

1 Supported in part by Grants PCM 84-09287 (S. M. S.) and PCM 83-41774 (V. L. S.) from the National Science Foundation.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1985 by the American Society of Plant Biologists