Plasma Membrane H+-ATPase in Guard-Cell Protoplasts from Vicia faba L. |
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Authors: | Shimazaki Ken-ichiro; Kondo Noriaki |
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Institution: | Division of Environmental Biology, The National Institute for Environmental Studies Yatabe-machi, Ibaraki 305, Japan |
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Abstract: | The activity of plasma membrane H+-ATPase was measured withmembrane fragments of guard-cell protoplasts isolated from Viciafaba L. ATP hydrolytic activity was slightly inhibited by oligomycinand ammonium molybdate, and markedly inhibited by NO3and vanadate. In the presence of oligomycin, ammonium molybdateand NO3, the ATP-hydrolyzing activity was strongly inhibitedby vanadate. It was also inhibited by diethylstilbestrol (DES),p-chloromercuribenzoic acid (PCMB) and Ca2+, but slightly stimulatedby carbonyl cyanide m-chlorophenylhydrazone (CCCP). The acitivityhad higher specificity for ATP as a substrate than other phosphoricesters such as ADP, AMP, GTP and p-nitrophenylphosphate; theKm was 0.5 mM for ATP. The activity required Mg2+ but was notaffected by K+, and it was maximal around pH 6.8. When guard-cellprotoplasts were used instead of membrane fragments, the ATPaseactivity reached up to 800µmol Pi.(mg Chl)1.h1in the presence of lysolecithin. These results indicate thatthe guard cell has a high plasma membrane H+-ATPase activity. (Received December 23, 1986; Accepted April 28, 1987) |
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