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Biochemical Contributors to Exercise Fatigue
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Arthur J. Cheng, Maja Schlittler, Håkan Westerblad
Glycogen breakdown is controlled by glycogen phosphorylase, which is regulated by covalent phosphorylation, allosteric regulation, and substrate availability (44). Phosphorylase exists in two forms: a phosphorylated form (referred to as phosphorylase a) that is considered to be constitutively active and a non-phosphorylated form (referred to as phosphorylase b) that is fully dependent on AMP for activation and is considered to be essentially inactive in resting muscle (13). Phosphorylation (activation) and dephosphorylation (inactivation) of phosphorylase are catalyzed by specific kinases and phosphatases, respectively (39). Glycogen synthesis is catalyzed by glycogen synthase, and the activity of this enzyme is controlled by phosphorylation in a complex manner (72).
Medicinal Plants in Natural Health Care as Phytopharmaceuticals
Published in Anil K. Sharma, Raj K. Keservani, Surya Prakash Gautam, Herbal Product Development, 2020
Studies have demonstrated the hypoglycaemic action and effects of coriander on carbohydrate metabolism. The effect of coriander seeds on carbohydrate metabolism was studied in rats that were fed with a fat-rich cholesterol diet. The spice exhibited noteworthy hypoglycemic action. There was an increase in the concentration of hepatic glycogen as was evident from the increased activity of glycogen synthase. Activities of glycogen phosphorylase and gluconeogenic enzymes revealed decreased rates of glycogenolysis and gluconeogenesis. The increased activities of glucose-6-phosphate dehydrogenase and glycolytic enzymes suggest the utilization of glucose by the pentose phosphate pathway and glycolysis. These observations clearly indicated that coriander seeds demonstrate good hypoglycemic activity through enhanced glycogenesis, glycolysis and decreased glycogenolysis and gluconeogenesis (Aissaoui et al., 2011).
Fuel Metabolism in the Fetus
Published in Emilio Herrera, Robert H. Knopp, Perinatal Biochemistry, 2020
The pathway of glycogen synthesis in the adult is summarized in Figure 6. It involves the activation of a glycogen synthase and the inhibition of a glycogen phosphorylase by mechanisms under the dependence of insulin and glucagon through cAMP-dependent pathways. Glycogen synthase and glycogen phosphorylase exist in active and inactive forms of which interconversion is catalyzed by phosphorylation/dephosphorylation processes under the control of specific kinases and phosphatases. Dephosphorylation of these two enzymes leads to glycogen synthase activation, glycogen phosphorylase inactivation, and glycogen synthesis. Moreover, glycogen phosphorylase in its active form is an inhibitor of the glycogen synthase phosphatase, thus precluding a concomitant synthesis and degradation of glycogen. glucose itself is able to stimulate glycogen synthesis because of the activation of glycogen phosphorylase phosphatase and inhibition of glycogen phosphorylase a, which blocks glycogen breakdown and facilitates glycogen synthesis.
Platelet glycogenolysis is important for energy production and function
Published in Platelets, 2023
Kanakanagavalli Shravani Prakhya, Hemendra Vekaria, Daniёlle M. Coenen, Linda Omali, Joshua Lykins, Smita Joshi, Hammodah R. Alfar, Qing Jun Wang, Patrick Sullivan, Sidney W. Whiteheart
A key enzyme needed to mobilize glucose from glycogen is glycogen phosphorylase.4 This enzyme removes terminal, α1–4-linked, glucoses from the polymer, generating glucose-1-phosphate that can be further metabolized by glycolysis.11 Glycogen phosphorylase exists in two interconvertible forms (a and b); the proportions of each are regulated by phosphorylation.12 Pharmacological inhibitors of glycogen phosphorylase have been developed to attenuate the hyperglycemia associated with diabetes, though their success has been limited because of bleeding complications.13,14 Two structurally related compounds, CP316819 and CP91149, inhibit GP by binding at the regulatory pocket.13 CP316819 is a more efficacious derivative of CP91149. These inhibitors principally bind to the less active b form and prevent its conversion to the more active a form.
Pre- and peripartal management of a woman with McArdle disease: a case report
Published in Gynecological Endocrinology, 2018
Tina Stopp, Michael Feichtinger, Wolfgang Eppel, Thomas M. Stulnig, Peter Husslein, Christian Göbl
Glycogen storage disease type 5, also called McArdle disease, is an autosomal recessive inherited disorder in muscle metabolism caused by the lack or dysfunction of muscle glycogen phosphorylase (myophosphorylase). Due to this condition the ability to break down glycogen into glucose subunits within the skeletal muscle during muscle activity is inhibited. This results in intolerance to strenuous exercise which manifests as fatigue, muscle stiffness and myalgia, in some cases accompanied by myoglobinuria and in severe instances renal failure due to muscle breakdown and rhabdomyolysis [1]. Most Patients experience a period of less painful and more effective exercise after an initial period of muscle cramps. The so-called ‘second wind phenomenon’ is typical of McArdle disease [2]. This phenomenon is believed to be caused by a switch to alternative sources of energy such as fatty acid oxidation and an increased blood flow to the muscle [3]. The metabolic shift is more effective when the patient’s muscles are conditioned through regular aerobic exercise [4].
Okra Modulates Regulatory Enzymes and Metabolites of Glucose-Utilizing Pathways in Diabetic Rats
Published in Journal of the American College of Nutrition, 2021
Joy Adaku Amadi, Peter Uchenna Amadi, Uche Chinedu Njoku
Diabetes affects the synthetic function of the liver with respect to glycogenesis. Our findings further buttressed this point, demonstrating that the depletion of glycogen stores is proportional to the severity of diabetes. This observation agrees with previous reports (40,41). Furthermore, glycogen phosphorylase and synthase, the two key regulatory enzymes of glycogen metabolism, were deranged. The glycogen phosphorylase activities rose at the initial diabetes stage and subsequently decreased possibly due to depletion of the glycogen stores while, as a result of poor glucose cellular uptake, glycogen synthase levels fell below the normal levels. From our observation, the okra sauce diet therapy was only partly successful in restoring alterations in glycogen metabolism.