Hexokinase and not glycogen synthase controls the flux through the glycogen synthesis pathway in frog oocytes
Here we set out to evaluate the role of hexokinase and glycogen synthase in the control of glycogen synthesis in vivo. We used metabolic control analysis (MCA) to determine the flux control coefficient for each of the enzymes involved in the pathway. Acute microinjection experiments in frog oocytes were specifically designed to change the endogenous activities of the enzymes, either by directly injecting increasing amounts of a given enzyme (HK, PGM and UGPase) or by microinjection of a positive allosteric effector (glc-6P for GS). Values of 0.61 +/- 0.07, 0.19 +/- 0.03, 0.13 +/- 0.03, and +/- 0.06 +/- 0.08 were obtained for the flux control coefficients of hexokinase EC 220.127.116.11 (HK), phosphoglucomutase EC 18.104.22.168 (PGM), UDPglucose pyrophosphorylase EC 22.214.171.124 (UGPase) and glycogen synthase EC 126.96.36.199 (GS), respectively. These values satisfy the summation theorem since the sum of the control coefficients for all the enzymes of the pathway is 0.87. The results show that, in frog oocytes, glycogen synthesis through the direct pathway is under the control of hexokinase. Phosphoglucomutase and UDPG-pyrophosphorylase have a modest influence, while the control exerted by glycogen synthase is null. (C) 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
|Título según WOS:||Hexokinase and not glycogen synthase controls the flux through the glycogen synthesis pathway in frog oocytes|
|Título según SCOPUS:||Hexokinase and not glycogen synthase controls the flux through the glycogen synthesis pathway in frog oocytes|
|Título de la Revista:||FEBS LETTERS|
|Editorial:||ELSEVIER SCIENCE BV|
|Fecha de publicación:||2013|
|Página de inicio:||2825|