title: Characterization of protein phosphatase 2A acting on phosphorylated plasma membrane aquaporin of tulip petals.
abstract: A protein phosphatase holo-type enzyme (38, 65, and 75 kDa) preparation and a free catalytic subunit (38 kDa) purified from tulip petals were characterized as protein phosphatase 2A (PP2A) by immunological and biochemical approaches. The plasma membrane containing the putative plasma membrane aquaporin (PM-AQP) was prepared from tulip petals, phosphorylated in vitro, and used as the substrate for both of the purified PP2A preparations. Although both preparations dephosphorylated the phosphorylated PM-AQP at 20 degrees C, only the holo-type enzyme preparation acted at 5 degrees C on the phosphorylated PM-AQP with higher substrate specificity, suggesting that regulatory subunits are required for low temperature-dependent dephosphorylation of PM-AQP in tulip petals.
authors.affiliation: Faculty of Life and Environmental Sciences, Shimane University, Shimane, Japan.
authors.forename: Abul Kalam
authors.initials: AK
authors.lastname: Azad
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shibata
mesh_terms: D020346:Aquaporins / Q000378:metabolism*; D035264:Flowers / Q000737:chemistry / Q000201:enzymology*; D007120:Immunochemistry; D019319:Okadaic Acid / Q000737:chemistry; D010749:Phosphoprotein Phosphatases / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D011479:Protamines / Q000737:chemistry; D054648:Protein Phosphatase 2; D031447:Tulipa / Q000737:chemistry / Q000201:enzymology*
chemical_list: D020346:Aquaporins; D011479:Protamines; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2