Protein phosphatase 1 catalyses the direct hydrolytic cleavage of phosphate monoester in a ternary complex mechanism.
The catalytic subunit of the Ser/Thr protein phosphatase 1 (PP1cat) hydrolyses N-acetyl Arg-Arg-Ala-phosphoThr-Val-Ala (K(M) = 3.7 mM) in a reaction that is inhibited competitively by inorganic phosphate (Pi, Ki = 1.6 mM) but unaffected by the product peptide alcohol at concentrations up to 3 mM. The enzyme does not catalyse the incorporation of 18O-label from 18O-labelled water into Pi whether, or not, the product alcohol is present. The dephosphorylated product alcohol of phosphorylated histone. an alternative substrate for the enzyme, serves as a competitive inhibitor for phosphopeptide hydrolysis (Ki = 60 microM) and co-mediates 18O-label exchange into Pi in a concentration-dependent manner (K(M) = 64 microM). These results indicate that hydrolysis occurs through the direct attack of an activated water molecule on the phosphate ester moiety of the substrate in a ternary complex mechanism.
School of Chemistry, The University of Birmingham, Edgbaston, UK.
J
J
Sanvoisin
D
D
Gani
D002384:Catalysis; D006868:Hydrolysis; D010710:Phosphates / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D054645:Protein Phosphatase 1
D010710:Phosphates; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1