Simulation of the activation of fat body glycogen phosphorylase and trehalose synthesis by peptide hormones in the American cockroach.
A model is described which simulates activation of glycogen phosphorylase and induction of trehalose synthesis in the fat body of the American cockroach, Periplaneta americana, by two hypertrehalosaemic peptides. Parameters for the model were estimated from literature data (Siegert et al., Insect Biochem. 16, 365), with the exception of the half-life of the physiologically active peptides, which was estimated from the model. The model describes satisfactorily the activation of glycogen phosphorylase and the increase of haemolymph carbohydrates, which is dependent on the activation of glycogen phosphorylase in the model. It further explains the observed differences in sensitivity for glycogen phosphorylase activation and increase in haemolymph carbohydrates by these peptides. Best fits were obtained with a physiological half-life of about 12-15 min for the peptides. This value is similar to what can be calculated from the in vivo effects of these peptides on heart beat (Gersch et al., Zool. Jb. Physiol. 86, 17), but it is considerably shorter than the published half-life of 1 h for radioactive peptide (Skinner et al., Insect Biochem. 17, 433). However, both values are compatible if part of the peptides in the haemolymph is not present in freely dissolved form, but bound to a haemolymph component. The model half-life would then represent the half-life of the free, physiologically active peptide, which was estimated from the disappearance of radioactive peptide to be about 12-15 min. This suggests, that the model half-life is realistic and physiologically more important than the half-life of radioactive peptide of 1 h.
Veenstra
J A
JA
Department of Biological Organic Chemistry, C.S.I.C., Barcelona, Spain.
D000818:Animals; D003058:Cockroaches / Q000378:metabolism*; D004187:Disaccharides / Q000096:biosynthesis*; D004789:Enzyme Activation; D005216:Fat Body / Q000201:enzymology*; D007301:Insect Hormones / Q000378:metabolism*; D008433:Mathematics; D008954:Models, Biological; D010455:Peptides / Q000378:metabolism; D006005:Phosphorylases / Q000378:metabolism*; D014199:Trehalose / Q000096:biosynthesis*
D004187:Disaccharides; D007301:Insect Hormones; D010455:Peptides; D014199:Trehalose; D006005:Phosphorylases