title: Modulation of the substrate specificity of the polycation-stimulated protein phosphatase from Xenopus laevis oocytes.
abstract: A polycation-stimulated (PCS) protein phosphatase was isolated in high yield (280 micrograms/100 g ovaries) from Xenopus laevis oocytes through a procedure involving a tyrosine-agarose hydrophobic chromatography. The 220-kDa enzyme contains a 35-kDa and a 62-kDa subunit. It was identified as the low-Mr polycation-stimulated (PCSL) protein phosphatase. The labile p-nitrophenyl phosphatase activity, copurifying with the phosphorylase phosphatase activity, can be increased severalfold by preincubating the purified enzyme with ATP, its analogues or PPi. This activation is time-dependent and accompanied by a parallel decrease of the phosphorylase phosphatase activity. Although the stimulation was antagonized by metal ions during the preincubation, the basal and ATP-stimulated p-nitrophenyl phosphatase requires Mg2+ or Mn2+ in the assay, with pH optima of 8.5-9 and 7.5 respectively.
authors.affiliation: Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Hermann
authors.forename: X
authors.initials: X
authors.lastname: Cayla
authors.forename: K
authors.initials: K
authors.lastname: Dumortier
authors.forename: J
authors.initials: J
authors.lastname: Goris
authors.forename: R
authors.initials: R
authors.lastname: Ozon
authors.forename: W
authors.initials: W
authors.lastname: Merlevede
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000302:isolation & purification / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002412:Cations; D004789:Enzyme Activation / Q000187:drug effects; D009865:Oocytes / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D011073:Polyamines; D000071228:Polyelectrolytes; D011108:Polymers / Q000494:pharmacology*; D013379:Substrate Specificity / Q000187:drug effects; D014982:Xenopus laevis
chemical_list: D009597:4-Nitrophenylphosphatase; D000255:Adenosine Triphosphate; D002412:Cations; D010749:Phosphoprotein Phosphatases; D011073:Polyamines; D000071228:Polyelectrolytes; D011108:Polymers