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Characterization of ATPase activities in rice root plasmalemma vesicles isolated by two‐phase partitioning
Author(s) -
Ros R.,
Sanz A.,
Segura J.,
Picazo I.
Publication year - 1991
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1991.tb01284.x
Subject(s) - vanadate , vesicle , chemistry , peg ratio , polyethylene glycol , sodium azide , sodium , atpase , chromatography , nuclear chemistry , aqueous solution , aqueous two phase system , biochemistry , membrane , enzyme , organic chemistry , finance , economics
Plasma membrane vesicles were isolated from the roots of 7‐day‐old rice plants ( Oryza sativa L. cv. Bahía) by utilizing an aqueous polymer two‐phase system with 6.2%:6.2% (w/w) Dextran T500 and polyethylene glycol 3350 (PEG) at pH 7.6. Plasmalemma vesicles of high purity were obtained as indicated by the vanadate‐sensitive K + , Mg 2+ ‐ATPase activity that was 18 times higher in the upper (PEG‐rich) phase than in the lower (Dextran‐rich) phase and by specific staining with sodium silicotungstate. Two peaks of ATPase activity were found. One showed a pH optimum at 6.0 in the presence of 150 m M KCl and 3 m M ATP with apparent K m (ATP) and V max of 0.75 m M and 79 μmol (mg protein) −1 h −1 , respectively. With 50 m M KCl and 7 m M ATP a pH optimum of 6.5, an apparent K m (ATP) of 6.3 m M and V max of 159 μmol (mg protein) −1 h −1 were determined. Both activities were specific for ATP, unspecific for monovalent cations, sensitive to sodium vanadate and Ca 2+ but insensitive to azide and nitrate.