Glucose metabolic fate

Coe and Bessell and coworkers studied the metabolic fates of 2-deoxy-2-fluoro-D-glucose (2DFG) and related compounds by using yeast hexokinase (as a model for mammalian hexokinase), and determined the kinetic constants K and V ) of the Michaelis-Menten equation D-glucose 0.17 (K in mAf)> 1 00 (relative value, D-glucose taken as 1) 2DG 0.59 0.11, 0.85 2DFG 0.19 0.03, 0.50 2-deoxy-2-fluoro-D-mannose (2DFM) 0.41 0.05, 0.85 2-deoxy-2,2-difluoro-D-nraZ>//Jo-hexose... 

We now turn to the metabolic fate of these sugars, fit most cells, the metabolic pathway responsible is termed glycolysis or the glycolytic pathway. The starting point for glycolysis is D-glucose. The end products of glycolysis... 

The substance glucuronic acid can be considered to be glucose with carbon 6 oxidized to the carboxylic acid level. Glucuronic acid /3-glycosides are the metabolic fate of a number of obnoxious compounds found in plants. Draw the structure of glucuronic acid. From its name can you guess where it was first found ... 

In the past, the main focus has been on insulin s effect on glucose uptake and hepatic glucose production. It now appears that there are many more players. The fate of glucose - or G6P - after uptake appears to be even more important for glucose metabolism, both in healthy persons and in patients with diabetes. There is an intimate interplay between the nutrient stores and between the different organs. This interplay appears well controlled, but the control is dynamic, so the detailed setup of the control system varies with the amount and type of nutrients. In this way the system can cope with almost any eating habit. 

By the third decade of the twentieth century, the emitted radioactivity from artificially synthesized tritium (3H) and carbon-14 (14C) was used to follow biochemical reactions. Glucose, amino acids, and other chemical compounds were synthesized with 3H or 14C incorporated either randomly or at some known position in the molecule. The radioactive products derived from radiolabeled glucose or amino acids added to cells, tissue slices, or a whole organism identified the metabolic fate of these molecules under defined... 

Lactate has two metabolic fates, either complete combustion to CO and H O or conversion back to glucose through gluconeogenesis. Both processes require an active ETS and oxidative phosphorylation. Reduced oxygenation of cells thus decreases the utilization of lactate and increases its production with a resulting lactic acidosis. 

The metabolic fate of glucose in the cytoplasmic space depends on a variety of factors. Beside the type of cells by which glucose is extracted from the extracellular compartment, factors like state of feeding, level of exercise, and the concentration of blood hormones known to exert an action on glucose metabolism, are involved in cellular glucose homeostasis (Devlin, 1992). 

Phosphoglucomutase converts glucose-l-phosphate into glucose-6-phosphate which has several metabolic fates. It is for example a precursor in the pentose phosphate pathway (PPP), it can be converted to a-D-glucose and to pyruvate via the glycolysis pathway (see Figure 9.2). 

Phosphoglucomutase converts glucose-1-phosphate into glucose-6-phosphate which has several metabolic fates. 

Recall What are four possible metabolic fates of glucose-6-phosphate ... 

With the development of stable, energy dense, isotonic lipid emulsions for intravenous use (Table IV), the use of concentrated glucose solutions which have to be infused through large calibre central veins has decreased. Administration of nutrients by peripheral vein eliminates the complications associated with central catheter placement and use (Jako-bowski et al., 1979). Intravenous fat emulsions are manufactured from either soyabean or safflower oil, stabilized with 1.2% egg phospholipid, and made isotonic with 2.5% glycerol. Formulations are rich in essential fatty acids, yield 1.1 kcal/ml, and have a metabolic fate which is similar to that of naturally occurring chylomicrons. Liposyn, however, has only trace amounts of linolenic acid compared to the two other emulsions. In addition, carnitine is absent from all of the lipid emulsions. 

Interest in the genetic engineering of both plants and micro-organisms for the production of tailor made amylose, amylopectin and/or starches has also been reported. Furthermore, investigations on the enzymatic modification of starch and its major components, for example the introduction of additional branches composed of glucose and/or other monosaccharides and/or uronic acids as well as amino acids or peptides, to produce carbohydrates of possibly comparable functionality to galactomannans, pectin, gum arable, etc., has been initiated. Also studies on the metabolic fate of carbohydrates in food, the biosynthesis of starch, the fine structure of starch from different sources, the effect of electrolytes on the gelatinization of starch and the development of enzymic methods for starch analyses are still active. 

Figure 3.5 The metabolic fate of a carbon-13 label traced through the two possible pathways for IPP biosynthesis when administered in the form of [1- C]-glucose. Iribel is indicated with a bold dot...

---