Open AccessModulation of the substrate specificity of the polycation‐stimulated protein phosphatase from Xenopus laevis oocytes
Author(s) -
HERMANN Jacques,
CAYLA Xavier,
DUMORTIER Kathelijn,
GORIS Jozef,
OZON René,
MERLEVEDE Wilfried
Publication year - 1988
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1988.tb13961.x
Subject(s) - xenopus , phosphatase , substrate (aquarium) , modulation (music) , microbiology and biotechnology , chemistry , biophysics , biology , biochemistry , phosphorylation , physics , ecology , gene , acoustics
A polycation‐stimulated (PCS) protein phosphatase was isolated in high yield (280 μg/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‐ M r polycation‐stimulated (PCS L ) 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 PP i . 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 Mg 2+ or Mn 2+ in the assay, with pH optima of 8.5–9 and 7.5 respectively.