Major pathways in carbohydrate metabolism in animals, excess glucose is converted to its storage form, glycogen, by glycogenesis. Glycogen metabolism and glycogen storage disorders kanungo. Muscle glycogen is not only a fuel source, but it is also a fuel sensor, a regulator of signaling pathways involved in training adaptation, and an influencer of intracellular osmolality. Liver glycogen can also contribute to the maintenance of normal blood glucose. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If both pathways were active simultaneously in a cell, there would be a futile cycle with cleavage of one p bond per cycle in forming udp.
Principles of metabolism pathways are not simple linear trajectories, but rather pathways are interconnected, complex, yet organized. The metabolism of the carbohydrates galactose, fructose, and glucose is intricately linked through interactions between different enzymatic pathways, and disorders that affect these pathways may have symptoms ranging from mild to severe or even lifethreatening. Glycogen synthesis is initiated from the transition of g6p to g1p. If the bloodglucose concentration increases after a glucose load, there is a very rapid change in glycogen metabolism in the liver, a switch from glycogen catabolism to glycogen synthesis. Glycogen is a very large, branched polymer of glucose residues. Let us first consider the steps in glycogen synthesis. Chem331 glycogen metabolism university of san diego.
These stored glycogen molecules can readily be degraded into glucose molecules and enter into the glycolytic pathway for energy. First, under aerobic conditions and at low atp high adp concentrations, glucose6p will rapidly be oxidized to co 2 via pyruvate and acetylcoa. Biochemistry glycogen metabolism flashcards quizlet. The reactions during this stage are responsible for converting more than 90 percent of the available food energy to a form that our bodies can use. Glycogen is a readily mobilized storage form of glucose. Brady department of medicine, committee on molecular metabolism. Thus, enzymatic defects along these pathways are associated with altered glucose metabolism and breakdown leading to hypoglycemia hepatomegaly and or liver disease in hepatic forms of glycogen storage disorder gsd and skeletal cardiac. Glycogen metabolism glycogenolysis pathway, enzymes and. Here, we provide an overview of glycogen metabolism and its regulation, with a focus on its role in metabolic reprogramming of cancer cells. And the two hormones that the body uses to regulate glycolysis and gluconeogenesis and pretty much, actually, all metabolic pathways, are insulin and another hormone called glucagon. Glycogen phosphorylase breaks a 1,4 linkage with a pi. Several pathways can be the source of g6p, including gluconeogenesis, glycogenolysis, and glycolysis 22,23.
Here, we show that glycogen metabolism is an important event that controls macrophage. This end product atp is a feed back inhibitor of glycogen. Regulation of glycogen metabolism roach major reference. Lesson on glycogen metabolism glycogenolysis pathway. In the lysosomes, glycogen degradation is catalyzed by. Aside from the purposeful manipulation of muscle glycogen concentration by diet and training nutrition periodization, periods of extended fasting during ramadan or in attempts to lose body weight result in metabolic responses that are usually contrary to maintaining high muscle glycogen concentrations, especially if training continues during. Metabolic disease disorders of carbohydrate metabolism. Glucagon and adrenaline stimulate glycogen degradation, while insulin stimulates the synthesis of glycogen. Pdf pathway of glycogen metabolism in methanococcus maripaludis. Glycolysis gluconeogenesis glycogen synthesis glycogenolysis.
Regulation of glycolysis and gluconeogenesis video. Biochemical and clinical aspects of glycogen storage diseases. Ninja nerds, join us in this video where we continue our discussion about glycogenolysis, and further expand on that concept where we talk about the regulation of glycogen metabolism. Oct 16, 2018 skeletal muscles use glycogen in a similar manner, however, typically after several minutes of strenuous activity to keep up with its energy requirements. Pentose phosphate pathway and glycogen metabolism glucose6phosphate is a key metabolite at the crossroad of four different pathways.
Glycogen breakdown and synthesis are regulated reciprocally, under hormonal control enzymatic activity minutes glycogen phosphorylase glycogen synthase example. When glucose is needed as a source of energy or as a precursor molecule in biosynthetic processes, glycogen. Pathway of glycogen metabolism in methanococcus maripaludis. Advances in the understanding of glycogen synthesis 47, 48 point to the initiation of synthesis. The complete breakdown of metabolites to carbon dioxide and water liberates. Liver glycogen primarily maintains blood glucose levels, while skeletal muscle glycogen is utilized during highintensity exertion, and brain glycogen is an emergency cerebral energy source. Learn pathways metabolism glycogen with free interactive flashcards. Glycogen phosphorylase glycogen phoshorylase catalyzes the following reaction. Regulation by hormones allows glygogen metabolism to adjust to the needs of the entire organism.
There are several enzymatic reactions andor pathways that utilize carbohydrates that need to be examined. Branches at about every tenth residue are created by. Glycogen is a polymer of glucose residues linked by. Glycogen metabolism uc berkeley mcb university of california. Hepatic glucose uptake, gluconeogenesis and the regulation. The anabolic pathway contrasting with glycogen breakdown is that of glycogen synthesis. Choice 6 is fictitious and does not occur in carbohydrate metabolism. When glucose is needed as a source of energy or as a precursor molecule in biosynthetic processes, glycogen is degraded by glycogenolysis.
Glycogen synthesis an overview sciencedirect topics. In the liver, glycogen synthesis and degradation are regulated to. Control of glycogen metabolism glycogen phosphorylase and glycogen synthase. Information partly derived from biochemistry by stryer and wikipedia.
The importance of glycogen metabolism is also highlighted by human genetic disorders that are caused by mutations in the enzymes involved. Fundamentals of glycogen metabolism for coaches and. Glycogen metabolism glycogen breakdown glycogen synthesis. Glycogen phosphorylase catalyzes phosphorolytic cleavage of the.
Stepbystep overview of the pathway, including regulation, advantages, and disadvantages of glycogenolysis, important enzymes glycogen. Remember that g6p can be 1 broken down in glycolysis, 2 converted to glucose by gluconeogenesis, and 3 oxidized in the pentose phosphate pathway. They focus on the biochemical pathways that we find in humans, and they also take into account some physiological and clinical aspects. Metabolites are produced and fed in a variety of directions at once.
The liver glycogen depot plays a central role in intermediary metabolism, storing and mobilising glycogen during the fed and fasted metabolic states, with these responses modulated during. Since the introduction of the muscle biopsy technique in the late 1960s, our understanding of the regulation of muscle glycogen storage and metabolism has advanced considerably. Choose from 500 different sets of pathways metabolism glycogen flashcards on quizlet. The activated kinase directly phosphorylates glycogen. Pdf in the human body, glycogen is a branched polymer of glucose stored mainly in. If both pathways were active simultaneously in a cell, there would bea futile cycle with cleavage of one p bond per cycle in formingudpglucose.
Glycogen phosphorylase was measured in the direction of the phosphorolysis of glycogen by coupling to phosphoglucomutase and glucose6phosphate dehydrogenase by the method of khandelwal et al. Glycogen synthesis requires a series of reactions that include glucose entrance into the cell through transporters, phosphorylation of glucose to glucose 6phosphate, isomerization to. Fat cannot be converted to glucose and maintain plasma glucose levels 4. While these conditions are not particularly common, they do shed some light on the physiological significance of glycogen metabolism. View enhanced pdf access article on wiley online library. Glucose metabolism is regulated at the points of glucose transport and at various points in the pathways of glycolysis and gluconeogenesis, including glycogen synthesis and breakdown. Within skeletal muscle and liver glucose is stored as glycogen. Just as cells reciprocally regulate glycolysis and gluconeogenesis to prevent a futile cycle, so too do cells use reciprocal schemes to regulate glycogen breakdown and synthesis. It is a very large, branched polymer of glucose residues figure 21. Most of the glucose residues in glycogen are linked by. Glycogen metabolism glycogen glycogen breakdown glycogen synthesis regulation.
The glycogen synthesis and breakdown pathway are highly regulated and, the synthesis. An indepth overview of glycogen synthesis, glycogen chemical structure, enzymes involved in synthesis, storage of glycogen and role of glycogen. The coenzyme required by glycogen phosphorylase is plp pyridoxal phosphate, derived from vitamin b6pyridoxine. A debranching enzyme is necessary because glycogen. Glycogen long chain of glucose units hooked together 1,4 linkage branched 1,6. Stores of readily available glucose, to supply the tissues of the body with an oxidizable energy source, are found as glycogen. Glycogen and glucose transform into one another through glycogen synthesis and degradation pathways. In the liver, glycogen synthesis and degradation are regulated to maintain. Glycogen synthesis pathway free download as powerpoint presentation. Mcmp 208 biochemistry for pharmaceutical sciences i april. Different pathways are used for the synthesis and degradation. Regulation organizes the flow of energy and metabolites. In the next step the phosphate is moved to the c6 position to give glucose 6phosphate, a cross road compound. Glycogen metabolism is also regulated by hormonally stimulated cascades that lead to the reversible phosphorylation of enzymes, which alters their kinetic properties.
Aug 12, 2012 glycogen metabolism detailed description with clinical significance slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Glucose6phosphate is the first step of the glycolysis pathway if glycogen. Glycogen is a polymer of glucose up to 120,000 glucose residues and is a primary carbohydrate storage form in animals. The clinical syndromes associated with these defects are referred to as glycogen storage diseases. Nov 26, 2017 lesson on glycogen metabolism glycogenolysis pathway. The glucose 6phosphatase system catalyzes the dephosphorylation of glucose 6phosphate to glucose, a necessary step for free glucose to leave the cell. Every metabolic pathway has a first committed step. Glycogen synthesis glycogen core started protein glycogenin uses primer 4 residues attached to phenolic oxygen of tyrosine. The synthesis of glycogen represents a key pathway for the disposal of excess glucose while its degradation is crucial for providing energy during exercise and times of need.
Glycogen long chain of glucose units hooked together 1,4 linkage. Regulation of glycogen metabolism in liver overview. The notes, and the corresponding slides, are also freely available in pdf. Glycogenolysis happens in the major storage organs of glycogen liver and muscle, when the body is need of more energy or when the blood glucose is low. Gluconeogenesis, glycogen metabolism, and the pentose.
Insulin control of the phosphorylation state of glycogen synthase and glycogen phosphorylase. Glycogen metabolism and glycogen storage disorders. Muscle glycogenolysis and rates of carbohydrate cho oxidation are affected by factors such as exercise intensity, duration, training status and substrate availability. The metabolism of the carbohydrates galactose, fructose, and glucose is intricately linked through interactions between different enzymatic pathways, and disorders that affect these pathways. Regulation of muscle glycogen metabolism during exercise. Stores of readily available glucose, to supply the tissues of the body with an oxidizable energy source, are found as glycogen, solely in the liver. The pathways of glycogen synthesis are separate from those of glycogen breakdown because there are two different enzyme systems.
This important control mechanism prevents glycogen from being synthesized at the same time that it is being broken down. Mutations in the genes encoding the enzymes involved in glycogen metabolism cause glycogen storage diseases. Glycogen metabolism glycogenolysis pathway, enzymes. Hormonal control of glycogen metabolism is similar to that of gluconeogenesis. Glycogen synthase kinase3 and glycogen phosphorylase. Gluconeogenesis, glycogen metabolism, and the pentose phosphate pathway objectives. Genetic defects have been described for several enzymes of glycogen metabolism. Effective glycogen metabolism is important during fasting and muscle contraction. The polymer is composed of units of glucose linked alpha14 with branches occurring alpha16 approximately every 812 residues. Glycogen synthesis pathway glycogen metabolic pathway. Carbohydrate metabolism biochemistry module biochemistry notes chain, followed by the addition of a phosphate group at c1.
In recent years, glycogen metabolism has also been demonstrated to be upregulated in many tumour types, suggesting it is an important aspect of cancer cell pathophysiology. The notes, and the corresponding slides, are also freely available in pdf and powerpoint formats. Regulation of glycogen metabolism february 5, 2003 bryant miles i. Regulation of glycogen metabolism wiley online library. Metabolic disease metabolic disease disorders of carbohydrate metabolism. The source of the glucose residues that form the glycogen particle is either the ingested food direct pathway of glycogen synthesis or the gluconeogenesis route indirect pathway, in which gluconeogenic precursors such as lactate and alanine produce glucose 6phosphate that may be used to synthesize glycogen. By both these mechanisms, glycogen degradation is integrated with glycogen synthesis. Glucose and glycogen convert into one another via synthesis or degradation through various steps in the glycogen metabolism pathways as presented schematically in figure 1. Brady department of medicine, committee on molecular metabolism and nutrition, the university of chicago, chicago, illinois. Oct 05, 2017 glycogen synthesis glycogenesis pathway lesson. The coordination is mainly dependent on hormonemediated and.
Glycogen metabolism biochemistry for medical students. Glycogen glycogen breakdown glycogen synthesis regulation. If you continue browsing the site, you agree to the use of cookies on this website. Glycogenolysis pathway, steps, diagram, stimulation. Our current understanding of how sugar metabolism affects inflammatory pathways in macrophages is incomplete. Chapter 16 lipid metabolism triacylglycerols tgs and glycogen are the two major forms of stored energy in vertebrates glycogen can supply atp for muscle contraction for less than an hour sustained work is fueled by metabolism. Metabolism regulation of glycogen metabolism youtube. Fundamentals of glycogen metabolism for coaches and athletes. Pathways are not simple linear trajectories, but rather pathways are interconnected, complex, yet. Glycogen synthesis and degradation homo sapiens wikipathways. Feb 20, 2017 glycogen metabolism lecture slides for mbbs ii students. Glucose metabolism an overview sciencedirect topics. Glycogen metabolism regulates macrophagemediated acute.
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