Insect fat body phosphorylase kinase is Ca2+-independent and acts even at 0 degrees C

Fat body glycogen phosphorylase in some overwintering insects is known to be activated by cold and, therefore, this enzyme acts as a key enzyme that regulates the production of glycerol or trehalose from glycogen during winter. In this paper we report the mechanism of phosphorylase activation by cold: the major phosphorylase kinase (EC 2.7.1.38) of fat body is bound to glycogen and functions at 0 degrees C, whereas phosphorylase phosphatase does not; thus this may cause a slow but continuous accumulation of the active form of phosphorylase in the cold.