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Acid phosphatases from beet root ( Beta vulgaris ) plasma membranes
Author(s) -
ArmientaAldana Eduardo,
González de la Vara Luis E.
Publication year - 2004
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.0031-9317.2004.00331.x
Subject(s) - phosphatase , acid phosphatase , membrane , okadaic acid , biochemistry , vanadate , chemistry , dusp6 , enzyme , size exclusion chromatography , chromatography , alkaline phosphatase , phosphate , protein phosphatase 2
Several acid phosphatases (EC 3.1.3.2) were found in beet root ( Beta vulgaris L.) plasma membranes. Two of them were partially purified by an extraction of plasma membranes with octylglucoside and successive gel‐filtration and anion‐exchange chromatographies. With p ‐nitrophenyl‐phosphate (pNPP) as substrate, most of the phosphatase activity was found in a fraction containing an 82‐kDa protein. This phosphatase showed an optimum pH of 5.4 and was inhibited by Cu 2+ , Zn 2+ , molybdate or vanadate. The other phosphatase had a lower specific activity with p NPP, but was able to dephosphorylate phospho‐myelin basic protein (phospho‐MBP). This phosphatase presented two polypeptides with molecular masses of 36 and 65 kDa and was 83% inhibited by 2 n M okadaic acid, which suggests it is a PP2A protein phosphatase. As the phosphatase activity was high in soluble (non‐membrane) fractions, the possibility that phosphatases in plasma membranes were soluble contaminants was assessed. Following the method of Bérczi and Møller (Plant Physiol. 116:1029, 1998), it was found that about 45% of both acid and protein phosphatase activities could be due to soluble enzymes trapped inside membrane vesicles.