title: Purification and characterization of protein phosphatase-1 from two cold-hardy goldenrod gall insects.
abstract: The catalytic subunit of protein phosphatase-1 (PP-1) was purified to homogeneity from final instar larvae (the overwintering stage) of freeze avoiding (Epiblema scudderiana) and freeze tolerant (Eurosta solidaginis) cold-hardy insects. Arrhenius plots showed that activity of PP-1 from both species was strongly suppressed at low temperature. Acidic shifts in pH optima and increased inhibition by okadaic acid were also observed when the enzymes were assayed at 4 degrees C compared with 24 degrees C. The data identify multiple ways by which PP-1 can be inhibited at low temperature and this inhibition appears to be key to sustaining high glycogen phosphorylase activity in support of polyol synthesis at low temperatures.
authors.affiliation: Institute of Biochemistry and Department of Chemistry, Carleton University, Ottawa, Ontario, Canada.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Pfister
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Storey
mesh_terms: D000818:Animals; D002846:Chromatography, Affinity; D003080:Cold Temperature; D004175:Diptera / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D005990:Glycerol / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D054645:Protein Phosphatase 1; D013012:Sorbitol / Q000494:pharmacology
chemical_list: D019319:Okadaic Acid; D013012:Sorbitol; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D005990:Glycerol