PHOSPHORYLASE ACTIVITIES IN PHARATE ADULT AND ADULT TOBACCO HORNWORMS, MANDUCA-SEXTA

Fat body glycogen phosphorylase in pharate adult and adult tobacco hor nworms, Manduca sexta, could only be activated transiently by the indi genous peptide hormone Mas-AKH. Chilling activated phosphorylase in vi tro which can be prevented by glucose; other mono- and disaccharides d id not reduce activation as much as glucose; derivatives of glucose we re also inactive in vitro, lit vivo glucose did not prevent phosphoryl ase activation during chilling when haemolymph concentrations were art ificially increased above 100mM. When glucose was injected into previo usly chilled animals, inactivation of the enzyme was induced even at 0 degrees C. In intact adults or in fat body pieces in vitro, chilling could only induce phosphorylase activation to 40-50%, but in homogenat es 70-90% active form was found after 2h at 25 degrees C when the kina se was allowed to be active; this is comparable to results obtained in ligated abdomens of larvae and indicates that the chemical nature of phosphorylase and phosphorylase kinase does not change during developm ent, Phosphorylase kinase from adult M. serta fat body was inactive at 0 degrees C or activating ligands are required. Mas-AKH does not seem to be a major agent in the activation of phosphorylase in adult M. se rta; enzyme activities can be modulated in vivo and in vitro by change s in glucose concentration of haemolymph or incubation medium. Copyrig ht (C) 1996 Elsevier Science Ltd