Kinetics of the Vacuolar H+-Pyrophosphatase
Open Access
- 1 December 1992
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 100 (4), 1698-1705
- https://doi.org/10.1104/pp.100.4.1698
Abstract
The responses of the vacuolar membrane (tonoplast) proton-pumping inorganic pyrophosphatase (H+-PPase) from oat (Avena sativa L.) roots to changes in Mg2+ and pyrophosphate (PPi) concentrations have been characterized. The kinetics were complex, and reaction kinetic models were used to determine which of the various PPi complexes were responsible for the observed responses. The results indicate that the substrate for the oat root vacuolar H+-PPase is Mg2PPi and that this complex is also a non-competitive inhibitor. In addition, the enzyme is activated by free Mg2+ and competitively inhibited by free PPi. This conclusion differs from that reached in previous studies, in which it was proposed that MgPPi is the substrate for plant vacuolar H+-PPases. However, models incorporating MgPPi as a substrate were unable to describe the kinetics of the oat H+-PPase. It is demonstrated that models incorporating Mg2PPi as the substrate can describe some of the published kinetics of the Kalanchoë daigremontiana vacuolar H+-PPase. Calculations of the likely concentrations of Mg2PPi in plant cytoplasm suggest that the substrate binding site of the oat vacuolar H+-PPase would be about 70% saturated in vivo.Keywords
This publication has 17 references indexed in Scilit:
- Regulation of Vacuolar H+-Pyrophosphatase by Free CalciumPlant Physiology, 1992
- Mechanisms of Magnesium TransportAnnual Review of Physiology, 1991
- H+‐translocating inorganic pyrophosphatase of plant vacuoles Inhibition by Ca2+, stabilization by Mg2+ and immunological comparison with other inorganic pyrophosphatasesEuropean Journal of Biochemistry, 1991
- Vacuolar proton‐pumping pyrophosphatase inBeta vulgaris shows vectorial activation by potassiumFEBS Letters, 1991
- An Essential Arginyl Residue in the Tonoplast Pyrophosphatase from Etiolated Mung Bean SeedlingsPlant Physiology, 1990
- Target Molecular Size and Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis Analysis of the ATP-and Pyrophosphate-Dependent Proton Pumps from Maize Root TonoplastPlant Physiology, 1989
- Electrogenic H+-Pumping Pyrophosphatase in Tonoplast Vesicles of Oat RootsPlant Physiology, 1986
- Chromatographic Resolution of H+-Translocating Pyrophosphatase from H+-Translocating ATPase of Higher Plant TonoplastPlant Physiology, 1986
- Kinetic model for the action of the inorganic pyrophosphatase from Streptococcus faecalisBiochemistry, 1985
- Proton-Translocating Inorganic Pyrophosphatase in Red Beet (Beta vulgaris L.) Tonoplast VesiclesPlant Physiology, 1985