title: Conversion of a phosphoseryl/threonyl phosphatase into a phosphotyrosyl phosphatase.
abstract: By use of the autophosphorylated epidermal-growth-factor receptor and the synthetic peptide RRLIE-DAEY(P)AARG, representing an autophosphorylation site of the transforming protein of Rous-sarcoma virus, it is demonstrated that the phosphotyrosyl phosphatase activity of the polycation-stimulated phosphatases is substantially increased by an enzyme-directed effect of ATP or PPi. Concomitant with this increase in phosphotyrosyl phosphatase activity, the phosphorylase phosphatase activity is decreased, thus dramatically changing the substrate specificity of these enzymes. The dephosphorylation of four different phosphotyrosyl sites of the epidermal-growth-factor receptor is neither consecutive nor at random, but a preferred dephosphorylation of the P1 site over the P3 greater than P2 greater than P4 sites is observed. This phosphatase activity represents a substantial fraction of the total phosphotyrosyl phosphatase activity in the post-mitochondrial supernatant of Xenopus laevis oocytes.
authors.affiliation: Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit te Leuven, Campus Gasthuisberg, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Goris
authors.forename: C J
authors.initials: CJ
authors.lastname: Pallen
authors.forename: P J
authors.initials: PJ
authors.lastname: Parker
authors.forename: J
authors.initials: J
authors.lastname: Hermann
authors.forename: M D
authors.initials: MD
authors.lastname: Waterfield
authors.forename: W
authors.initials: W
authors.lastname: Merlevede
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases; D013379:Substrate Specificity
chemical_list: D010455:Peptides; C047660:arginyl-arginyl-leucyl-isoleucyl-glutamyl-aspartyl-alanyl-glutamyl-tyrosyl-alanyl-alanyl-arginyl-glycine; D000255:Adenosine Triphosphate; D066246:ErbB Receptors; D010749:Phosphoprotein Phosphatases; D017027:Protein Tyrosine Phosphatases