Glucose ATP and

Fig. 6.22. The (a) 1-D and (b) 2-D-DOSY spectrum of a mixture containing D2O, glucose, ATP and SDS micelles [50]. (Adapted with permission from ref. [50]. Copyright 1993 American Chemical Society), (c) 1-D and (d) 2D-DOSY spectrum of the perchloric acid extract of a gerbil brain in D2O. Selected assignments are ac — acetate ala — alanine cho — choline cr — creatinine etn — ethanolamine GABA — y-aminobutyric acid glu — glutamine CPC — glycerophospho-choline lac — lactate m-ino — myo-inositol NAA — N-acetylaspartate succ — succinate and tau = taurine [51]. (Adapted with permission from ref. [51]. Copyright 1997 Elsevier.)...

In this method an appropriate enzyme (e.g., GPDase) and the antigen are co-immobilized on a solid phase. Hexokinase-labeled antibody produces an accelerated conversion of glucose, ATP and NAD+ since the enzymes are in each other s vicinity. 

Fig. 27. Concentration distributions of glucose, ATP, and pyruvate four seconds after a glucose pulse onto the liquid surface...

The results of one of the first multistep enzyme systems to be immobilized were presented in 1970 by Mosbach and Mattiasson (3). They covalently bonded hexokinase (HK) and glucose-6-phosphate dehydrogenase (G-6-PDH) to individual polymer particles via the cyanogen bromide reaction. Using a solution containing glucose, ATP and NADP" ", they demonstrated that the coimmobilized enzymes formed product... 

Glucose [50-99-7] urea [57-13-6] (qv), and cholesterol [57-88-5] (see Steroids) are the substrates most frequentiy measured, although there are many more substrates or metaboUtes that are determined in clinical laboratories using enzymes. Co-enzymes such as adenosine triphosphate [56-65-5] (ATP) and nicotinamide adenine dinucleotide [53-84-9] in its oxidized (NAD" ) or reduced (NADH) [58-68-4] form can be considered substrates. Enzymatic analysis is covered in detail elsewhere (9). 

Phosphate esters of glucose, fructose, and other monosaccharides are important metabolic intermediates, and the ribose moiety of nucleotides such as ATP and GTP is phosphorylated at the 5 -position (Figure 7.13). 

Pyruvate kinase possesses allosteric sites for numerous effectors. It is activated by AMP and fructose-1,6-bisphosphate and inhibited by ATP, acetyl-CoA, and alanine. (Note that alanine is the a-amino acid counterpart of the a-keto acid, pyruvate.) Furthermore, liver pyruvate kinase is regulated by covalent modification. Flormones such as glucagon activate a cAMP-dependent protein kinase, which transfers a phosphoryl group from ATP to the enzyme. The phos-phorylated form of pyruvate kinase is more strongly inhibited by ATP and alanine and has a higher for PEP, so that, in the presence of physiological levels of PEP, the enzyme is inactive. Then PEP is used as a substrate for glucose synthesis in the pathway (to be described in Chapter 23), instead... 

The citric acid cycle, a nine-step process, also diverts chemical energy to the production of ATP and the reduction of NAD and FAD. In each step of the citric acid cycle (also known as the Krebs cycle) a glucose metabolite is oxidized while one of the carrier molecules, NAD or FAD, is reduced. Enzymes, nature s chemical catalysts, do a remarkable job of coupling the oxidation and reduction reactions so that energy is transferred with great efficiency. 

To correlate embryonic arrests with the metabolic pathways, and especially to understand why cellular organelles first undergo chemical damages, biological investigations include evaluation of DNA, RNA, protein, glucose, lipid, and adenosine-5 -triphosphate (ATP) contents, whose fractions are extracted and isolated by modified Schneider methods. In particular,... 

The pentose phosphate pathway is an alternative route for the metabolism of glucose. It does not generate ATP but has two major functions (1) The formation of NADPH for synthesis of fatty acids and steroids and (2) the synthesis of ribose for nucleotide and nucleic acid formation. Glucose, fructose, and galactose are the main hexoses absorbed from the gastrointestinal tract, derived principally from dietary starch, sucrose, and lactose, respectively. Fructose and galactose are converted to glucose, mainly in the liver. 

Another common procedure which is used for glucose assay is the hexokinase procedure in which the glucose is phosphory-lated by means of ATP and then dehydrogenated with glucose-6-phosphate dehydrogenase measuring the abosrption of NADPH... 

Metabolic pathways interconnect glycogen, fat, and protein reserves to store and retrieve ATP and glucose. 

Protein phosphorylation in response to rising cAMP levels activates enzymes involved in maintaining blood glucose levels and in making ATP. 

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