title: Removal of phosphate from phosphohistidine in proteins.
abstract: Kinetic constants of KM = 0.8 microM, 3 microM and 1.6 microM, and kcat = 9 s-1, 7 s-1 or 9 s-1 were determined for histidine dephosphorylation by protein phosphatases 1, 2A and 2C respectively. IC50 values were determined for the inhibition of protein phosphatase 1 by inhibitor 1 (IC50 = 1 nM), inhibitor-2 (IC50 = 3 nM) and okadaic acid (IC50 = 30 nM) and for the inhibition of protein phosphatase 2A by okadaic acid (IC50 = 0.02 nM) and microcystin-LR (IC50 = 1 nM). Inhibitor-1 (Ki = 0.7 nM) and okadaic acid (Ki = 32 nM) are noncompetitive with protein phosphatase 1. Some of the IC50 values were low enough to violate the assumptions of the usual inhibition equations and a more general approach to the analysis of the data was used. On the basis of these kinetic parameters and the presence of phosphohistidine, the major cellular protein serine/threonine phosphatases are likely to act as protein histidine phosphatases in the cell.
authors.affiliation: Department of Biological Chemistry, University of California at Davis 95616, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Kim
authors.forename: K H
authors.initials: KH
authors.lastname: Pesis
authors.forename: H R
authors.initials: HR
authors.lastname: Matthews
mesh_terms: D000818:Animals; D004988:Ethers, Cyclic / Q000494:pharmacology; D006639:Histidine / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D008387:Marine Toxins; D052998:Microcystins; D019319:Okadaic Acid; D010456:Peptides, Cyclic / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D011817:Rabbits
chemical_list: D004988:Ethers, Cyclic; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; D010710:Phosphates; D019319:Okadaic Acid; D006639:Histidine; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; C057862:cyanoginosin LR; C005436:phosphohistidine