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LIGHT‐INDUCIBLE ABSORBANCE CHANGES AND VANADATE‐SENSITIVE ATPase ACTIVITY ASSOCIATED WITH THE PRESUMPTIVE PLASMA MEMBRANE FRACTION FROM CAULIFLOWER INFLORESCENCES
Author(s) -
Caubergs Roland J.,
Asard Han H.,
DeGreef Jan A.,
Leeuwerik Frans J.,
Oltmann Fred L.
Publication year - 1986
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1986.tb04720.x
Subject(s) - vanadate , chemistry , atpase , microsome , membrane , biochemistry , absorbance , chromatography , biophysics , enzyme , biology
Sucrose density gradient centrifugation of a microsomal membrane fraction of cauliflower inflorescences showed a strong correlation between a blue light mediated cytochrome b reduction (LIAC) and an ion stimulated nitrate‐insensitive but a vanadate‐sensitive ATPase activity at 38‐40% sucrose. LIAC activity and vanadate‐sensitive ATPase might be assigned to the same type of membrane different from ER, Golgi, tonoplast and mitochondria. The Mg 2+ ‐dependent ATP‐hydrolytic activity obtained after purification of the microsomal fraction on an aqueous polymer two phase system was partially characterized. Temperature optimum (40°C), pH optimum (pH 7.0), vanadate inhibition (I 50 at 20 μ M ), substrate kinetics ( K m = 1.37 m M Mg.ATP) and inhibitor studies all point to the presence of the frequently described plasma membrane ATPase. Potassium and Na + stimulated the enzyme activity (20‐40%). In general our data arc strongly in favour of the hypothesis that LIAC activity is localized on the plant plasma membrane. The cytochrome b involved in the light reaction has a midpoint potential near +150 mV. This cytochrome which has been previously shown in a cauliflower microsomal fraction is a constituent of the plasma membrane.