A D-Glucose-l-phosphate

FIGURE 7.23 The starch phosphorylase reaction cleaves glucose residues from amy-lose, producing a-D-glucose-l-phosphate. 

The fact that this disaccharide, like sucrose, is formed as a result of de-phosphorolytic condensation involving a-D-glucose-l-phosphate supports the view that D-glucose also exists in this disaccharide as the a-form. 

L-Araboketose, enzymatic reaction with a-D-glucose-l-phosphate, V, 41 L-Araboketoside, a-D-glucopyranosyl-, V, 35, 41... 

McCready, R. M., and Hassid, W. Z. (1957). Preparation of a-D-Glucose-l-Phosphate by Means of Potato Phosphorylase. Methods Bnzymol 3 137. 

The reaction mixture contained in a total volume of 300 /xL 15 /xmol Tris-HC1 buffer (pH 8.0), 3.6 /xmol of MgCfe, 7.2 fimol of a-D-glucose-l-phosphate, 1.8 /xmol of dTTP, 1.8 units of inorganic pyrophosphatase, and 30 /xL of appropriately diluted enzyme. The mixture was incubated at 37°C. Samples (36 /xL) were withdrawn at timed intervals up to 20 minutes, and the reaction was terminated by mixing with 1.0 mL of 50 mM potassium phosphate (pH... 

The previous study of the acid-catalysed hydrolysis of the series of deoxyfluoro- and deoxy-a-D-glucose-l-phosphate analogues has amply demonstrated the Importance of electronic effects from such substituents on reactions proceeding via cationic transition states. As was seen In Scheme 1, this enzymic reaction Is also thought to proceed via oxocarbonlum lon-llke transition states. On the basis of electronic effects alone, therefore, the deoxy substrates would be expected to turn over more rapidly than the normal substrate and the deoxyfluoro substrates more slowly. 

The vine-twining polymerization is a method for the preparation of well defined supramolecules, which are amylose pol5mer inclusion complexes (70). The method consists of the enz5matic pol5meriza-tion of a-D-glucose-l-phosphate catalyzed by phosphorylase in the presence of various S mthetic pol mers such as polyethers, polyesters, poly(ester ether)s, and amphiphilic block copol5mers. The IH-NMR spectra of the polymers indicated structures composed from amylose and guest pol mers. 

This is a phosphorylase-catalyzed enzymatic pol5rmerization of an a-D-glucose-l-phosphate from a maltoheptose in the presence of polycarbonates. Polycarbonates with a shorter methylene chain length such as poly(tetramethylene carbonate) is more favorable as the guest polymer to form the inclusion complex with amylose. 

Phosphorylases catalyze the phosphorolytic cleavage of a-D-glucose-l-phosphate from the non-reducing end of the amylose molecule. 

Phosphorylase cleavage of a-D-glucose-L-phosphate from the nonreducing end of the aiiu losc... 

The C- and P- n.m.r. spectra of a single crystal of dipotassium a-D-glucose-l-phosphate dlhydrate for different orientations in the external magnetic field have been recorded in the course of an application of a c- H, P) triple resonance technique to the determination of C and -P shielding tensors. " ... 

Certain species of bacteria, namely. Pseudomonas sacckarophUa, Pseudomonas ptdrifadens, and Leicconostoc mesenteroides, contain a phos-phorylase which, in the presence of inorganic phosphate, catalyzes the phosphorlytic decomposition of the disaccharide, sucrose, with the production of a-D-glucose-l-phosphate and D-fructose. The reverse reaction, the dephosphorolytic condensation of a-D-glucose-l-phosphate and D-fructose results in the formation of sucrose with the elimination of phosphoric acid, as shown in Fig. 2. 

The synthetic process can be regarded as a condensation reaction in which the elements of water of hydrolysis are replaced by those of phosphoric acid. The process can also be considered as a transglucosidation reaction in which the glucosidic radical from the a-D-glucose-l-phosphate is transferred to a fructofuranoside radical, serving as an acceptor. 

The fact that sucrose can be synthesized from a-D-glucose-l-phosphate and D-fructose is in accord with the evidence brought forward by Isbell and Pigman and by Gottschalk that D-fructose exists as an equilibrium mixture of the pyranose and furanose forms. The total system of sucrose synthesis can be represented by the equation (Fig. 2), which includes the... 

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