Carbohydrates glycogen and

Fig. 1.4. Structure of starch and glycogen. Starch, our major dietary carbohydrate, and glycogen, the body s storage form of glucose, have similar structures. They are polysaccharides (many sugar units) composed of glucose, which is a monosaccharide (one sugar unit). Dietary disaccharides are composed of two sugar units.

The reference values for common metabolites in the diagnosis of carbohydrate disorders are shown below. The disorders of carbohydrate and glycogen metabolism are either confirmed by enzyme assay or DNA analysis. Reference values for enzymes have been variable, depending on the assaying conditions however, the diagnostic value usually falls below 5-10% of normal. 

Most carbohydrates exist in the form of polysaccharides. Polysaccharides give stmcture to the cell walls of land plants (cellulose), seaweeds, and some microorganisms and store energy (starch in plants and glycogen in animals). They are important in the human diet and in many commercial apphcations. 

Since D-fructose and D-glucose phosphates are amongst the first products of photosynthesis, and since starch (in plants) and glycogen (in animals) are converted by phosphorylase to D-glucosyl phosphate, biosynthesis of carbohydrates revolves around these ubiquitous compounds... 

Aqueous suspensions of 6-methyluracil, when administered orally to rats, accelerate and intensify the assimilation of alimentary carbohydrates and increase hepatic glycogen synthesis [267]. 

Carbohydrates mainly occur in food in the form of polymers (starches and glycogen). They are cleaved by pancreatic amylase into oligosaccharides and are then hydrolyzed by glycosidases, which are located on the surface of the intestinal epithelium, to yield monosaccharides. Glucose and galactose are taken up into the enterocytes by secondary active cotransport with Na"" ions (see p. 220). In addition, monosaccharides also have passive transport systems in the intestine. 

Amylase, the most important endoglyco-sidase in the pancreas, catalyzes the hydrolysis of al 4 bonds in the polymeric carbohydrates starch and glycogen. This releases maltose, maltotriose, and a mixture of other oligosaccharides. 

Mechanism of Action Acts as a coenzyme for various metabolic functions, including metabolism of proteins, carbohydrates, and fats. Aids in the breakdown of glycogen and in the synthesis of gamma-aminobutyric acid in the CNS. Therapeutic Effect Prevents pyridoxine deficiency. Increases the excretion of certain drugs, such as iso-niazid, that are pyridoxine antagonists. 

Enzymes. See also, Amylases, Galactosi-dases, /3-Glucuronidase, Glyco-enzymes, a-D-Mannosidase. acting on pectic substances, 5, 79-102 degradation by, of starch and glycogen, 3, 251-310 17, 407-430 of glycoprotein structure, 27, 301-341 specificity of, in the domain of carbohydrates, 5, 49-78... 

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