Hormonal Regulation of Adipocyte Enzymes

作者：John C. Khoo, Daniel Howard Steinberg, Barbara L. Thompson, Steven E. Mayer · 发表于：Journal of Biological Chemistry · 年份：1973 · DOI：10.1016/s0021-9258(19)43808-8 · 被引用次数：114 · 研究领域：Muscle metabolism and nutrition、Metabolism, Diabetes, and Cancer、Adipose Tissue and Metabolism

Abstract The effects of epinephrine and insulin on three enzyme systems in adipocytes were investigated with regard to the role of adenosine 3',5'-monophosphate (cyclic AMP) in their control and the possibility that differential regulatory mechanisms might operate beyond cyclic AMP. When rat adipocytes were incubated with increasing concentrations of epinephrine (0.01 to 100 µm) elevation of cyclic AMP and glycerol production, activation of phosphorylase and deactivation of glycogen synthase appeared to be closely correlated. Activatability of hormone-sensitive in cell extracts by cyclic AMP-dependent protein decreased with increasing concentrations of epinephrine indicating conversion of the nonactivated to the activated form during incubation of the cells. Activation of in cell-free extracts by cyclic AMP and MgATP was promptly arrested by addition of protein inhibitor. This finding, together with results of previous studies, rules against the involvement of a lipase kinase analogous to that of phosphorylase in phosphorylase activation. Phosphorylase activities measured between pH 6.0 and 9.2 were unaffected at any concentration of epinephrine. Moreover, activation of phosphorylase in cell-free extracts was not inhibited by addition of protein inhibitor. When adipocytes were incubated in Ca2+-free Krebs-Ringer bicarbonate medium, activation of phosphorylase in response to epinephrine was not impaired. Phosphorylase assayed in cell-free extracts did not require Ca2+ for the ...