A theoretical study of effects of cytosolic Ca2+ oscillations on activation of glycogen phosphorylase.
Taking into account the Ca(2+)-stimulated degradation of inositol 1,4,5-trisphosphate (IP(3)) by a 3-kinase, we have theoretically explored the effects of both simple and complex Ca(2+) oscillations on the regulation of a phosphorylation-dephosphorylation cycle process involved in glycogen degradation by glycogen phosphorylase a-form, respectively. For the case of simple Ca(2+) oscillations, the roles of cytosolic Ca(2+) oscillations in the regulation of active phosphorylase depend upon the maximum rate of IP(3) degradation by the 3-kinase, V(M5). In particular, the smaller the values of V(M5) are, the lower the effective Ca(2+) threshold for the activation of glycogen phosphorylase will be. For the case of complex Ca(2+) oscillations, the average level of fraction of active phosphorylase is nearly independent from the level of stimulation increasing in the bursting oscillatory domain. Both simple and complex Ca(2+) oscillations can contribute to increase the efficiency and specificity of cellular signalling, and some theoretical results of activation of glycogen phosphorylase regulated by Ca(2+) oscillations are close to the experimental results for gene expression in lymphocytes.
Rozi
Anvar
A
Department of Physics, Central China Normal University, Wuhan 430079, Hubei, PR China.
Jia
Ya
Y
D020013:Calcium Signaling; D004789:Enzyme Activation / Q000187:drug effects; D024981:Glycogen Phosphorylase / Q000378:metabolism*; D006728:Hormones / Q000494:pharmacology; D007700:Kinetics; D008954:Models, Biological; D013997:Time Factors
D006728:Hormones; D024981:Glycogen Phosphorylase