Pfister, T.D. and Storey, K.B. 2002. Purification and characterization of protein phosphatase-1 from two cold-hardy goldenrod gall insects. Arch. Insect Biochem. Physiol. 49, 56-64.

Purification and Characterization of Protein Phosphatase-1 from Two Cold-hardy Goldenrod Gall Insects.

Thomas D. Pfister and Kenneth B. Storey


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 4C compared with 24C. 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.