Free glucose

Figure 15-5. Transport and fate of major carbohydrate and amino acid substrates and metabolites. Note that there is little free glucose in muscle, since it is rapidly phosphorylated upon entry.

The third indirect route involves the formation of free glucose from glucose 6phosphate by circumventing the hexokinase reaction. This route is catalyzed by... 

The free glucose produced by this reaction is supplied to the blood from the tissues. As exemplified by gluconeogenesis, one may easily envision the economical organization of these metabolic routes, since, apart from four special gluconeogenesis enzymes-pyruvate carboxylase, phosphopyruvate carboxylase, fructose bisphosphatase, and glucose 6-phosphatase-individual glycolytic enzymes are also used in the gluconeogenesis. 

J. Wang, J. Liu, L. Chen, and F. Lu, Highly selective membrane-free, mediator-free glucose biosensor. Anal. Chem. 66, 3600-3603 (1994). 

Zhou, X., et al., Facile synthesis of nanospindle-like Cu20/straight multi-walled carbon nanotube hybrid nanostructures and their application in enzyme-free glucose sensing. Sensors and Actuators B Chemical, 2012.168 p. 1-7. 

Hydrolyzes the a-1,6 bond, releasing the single residue at the branch point as free glucose. This represents the only free glucose produced directly in glycogenolysis. 

Glucose 6-phosphatase releases free glucose only in liver... 

Required to release free glucose from tissue... 

Figure 2.26 (a) Scheme for an electrostatically self-assembled multilayer (PAHOs)4(Apo-COx)3(COx) electrode, (b) Catalytic current response to p-d-glucose concentration for self-assembled nanostructured thin films of PAH-Os/COx/(PAH-Os/(ApoGOx)3 and (PAH-Os/ApoCOx)3/PAH-Os/COx, where ApoCOx is FAD-free glucose oxidase. Taken from Ref [219]. 

C. As glucose is consumed by cellular metabolism, glycogen is degraded (glycogenolysis) to form free glucose in an effort to maintain relatively constant blood glucose levels. 

This enzyme is mainly found in liver and kidney, the only two organs capable of releasing free glucose into the blood. 

Figure 18. Bienzyme multilayers for interferent-free glucose sensors.

The glucose 1-phosphate so formed can be used for ATP synthesis in muscle or converted to free glucose in the liver. Glycogen phosphorylase occurs in two forms the more active phosphorylase a and the less active phosphorylase b (Fig. 6-31). Phosphorylase a has two subunits, each with a specific Ser residue that is phosphorylated at its hydroxyl group. These serine phosphate residues are required for maximal activity of the enzyme. 

Hexokinase, which catalyzes the entry of free glucose into the glycolytic pathway, is a regulatory enzyme. There are four isozymes (designated I to IV), encoded... 

Cellular Glucose Concentration The concentration of glucose in human blood plasma is maintained at about 5 mM. The concentration of free glucose inside a myocyte is much lower. Why is the concentration so low in the cell What... 

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