首页 | 本学科首页   官方微博 | 高级检索  
     


Regulation of glycogen phosphorylase in fat body ofCecropia silkmoth pupae
Authors:Rolf Ziegler   Masaaki Ashida   Ann M. Fallon   L. T. Wimer   S. Silver Wyatt  G. R. Wyatt
Affiliation:(1) Department of Biology, Queen's University, K7L 3N6 Kingston, Ontario, Canada;(2) Present address: Department of Biology, University of Tokyo, Faculty of General Education, Meguro-ku, Tokyo, Japan;(3) Present address: Department of Entomology, Texas A and M University, 77843 College Station, Texas, USA;(4) Present address: Department of Biology, University of South Carolina, 29208 Columbia, South Carolina, USA;(5) Present address: Institut für Tierphysiologie und Angewandte Zoologie, Freie Universität Berlin, Grunewaldstraße 34, D-1000 Berlin 41
Abstract:Summary Glycogen phosphorylase of pupal fat body of the silkmoth,Hyalophora cecropia, and its activation by different stimuli have been studied. Spectrophotometric assay in the direction of glycogenolysis, used in most of the experiments, indicated higher amounts of phosphorylasea than assay by release of Pi from glucose-1-phosphate; both assays, however, estimated changes in proportion of phosphorylasea equally. TheK ms for Pi were estimated as 5 mM for phosphorylasea in the absence of AMP and 18 mM for phosphorylaseb with 2 mM AMP.When diapausing pupae were held at 4°C, fat body phosphorylase was quickly activated by conversion to thea form up to about 50% of the total, and then declined again after 30 days, when glycerol had accumulated in the hemolymph. Cold activation in vivo was quickly reversed at 25°C. Removal of the brain did not prevent cold activation. After storage at 15°C, sensitivity to cold activation was diminished. Locusts and crickets also showed activation of phosphorylase after chilling.Exposure of fat body to air, transfer to Ringer solution, or physical agitation, caused activation of phosphorylase which is classed as ldquoshockrdquo activation. After about 1 h incubation in Ringer at 25°C, this effect reversed spontaneously. Activation also occurred in fat body in vitro after transfer to 0°C (ldquocoldrdquo activation), and was reversed at 25°C. The previously reported inhibition of activation by glycerol, however, could not be consistently reproduced.In fat body homogenates, phosphorylaseb was converted to phosphorylasea by incubation with ATP and Mg2+, which indicates activity of phosphorylase kinase. In preparations treated with Sephadex G-25 and then incubated, the reverse conversion took place, which was inhibited by fluoride, and indicates activity of phosphorylase phosphatase.Cyclic AMP added to fat body in vitro, or theophylline either in vivo or in vitro, stimulated the activation of phosphorylase. In fat body in vitro, shock activation was paralleled by elevation of tissue cyclic AMP, whereas cold activation was not. Cyclic GMP did not stimulate activation, and showed no significant changes in tissue levels.It is concluded that the conversion of silkmoth pupal fat body phosphorylaseb to phosphorylasea can be stimulated by a shock-initiated mechanism involving cyclic AMP and a distinct cold-initiated mechanism independent of cyclic AMP.Abbreviations DTT dithiothreitol - cyclic AMP 3prime,5prime-cyclic adenosine monophosphate - cyclic GMP 3prime,5prime-cyclic guanosine monophosphate - P i inorganic phosphate This investigation was begun in the Department of Biology, Yale University, New Haven, Connecticut, USA
Keywords:
本文献已被 SpringerLink 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号