Phosphate esters hexoses

Phosphate esters of 2-deoxy D-galactose (2-deoxy-D-Zt/xo-hexose) have also been obtained (15). The 6-phosphate (12) was synthesized from the methyl glycoside (9) by condensing the latter with acetone the 3,4-... 

Hexose 6-phosphate, 3-deoxy-D-nho Hexose 6-phosphate, S-deoxy-D-xylo-Hexose, phosphate esters of... 

It is well-known that in plant tissues certain amounts of flavour compounds are bound as non-volatile sugar conjugates. Most of these glycosides are jS-glu-cosides, but there are other glycones like pentoses, hexoses, disaccharides and trisaccharides too [46]. Acylated glycosides and phosphate esters have also been reported [47, 48]. Information about the analysis of glycosides can be found in the work of Herderich et al. [49]. 

Calvin and coworkers, in their classical studies of photosynthetic processes, detected labeled triose phosphates and hexose phosphates on bi-dimensional chromatograms, using phenol-water and 1-butanol-pro-pionic acid-water as solvents.120121 In addition to the detection of radioactivity, an ammonium molybdate-nitric acid color reagent was used to detect phosphorus.16 Acidic-solvent developers were used to obviate decomposition of the esters. 

The second reaction (in which NADPH is formed) functions as the indicator reaction. Although the hexokinase reaction is relatively nonspecific and acts on hexoses other than glucose (Chapter 13) to form 6-phosphate esters, the indicator reaction is specific for glucose 6-phosphate making the overall assay procedure highly specific for glucose. 

In contrast, sucrose (common table sugar), a disaccharide, is synthesized in the cytosol. Plants lack the ability to transport hexose phosphates across the chloroplast membrane, but an abundant phosphate translocator mediates the transport of triose phosphates from chloroplasts to the cytosol in exchange for phosphate. Fructose 6-phosphate formed from triose phosphates joins the glucose unit of UDP-glucose to form sucrose 6-phosphate (Figure 20.13). Hydrolysis of the phosphate ester yields sucrose, a readily... 

Monosaccharides. M. are linear polyhydroxyalde-hydes (aldoses) or polyhydroxyketones (ketoses). Most important among M. are the pentoses (CjHiqO,) and hexoses (C6H,20 ). Important aldopentoses include, e.g., D- ribose, D- xylose, and L- arabinose. Important aldohexoses include D- glucose, D- man-nose, and D- galactose the major ketohexoses are D- fructose and sorbose. The 6- deoxy sugars L- fu-cose and L- L-rhamnose are also widely distributed hexoses. M. with more carbon atoms (heptoses 7 carbon atoms, octoses, etc.) or less carbon atoms (trioses 3 carbon atoms) do not occur in the free form in organisms but do play a role in carbohydrate metabolism as phosphate esters tetroses (4 carbon atoms) erythrose, threose are relatively rate. 

This reaction was recognized as a potential intracellular source of deoxyribose 1-phosphate because the mutase-catalyzed interconversion of 1-and 5-phosphate esters of deoxyribose was known. Boxer and Shonk (25) showed that extracts of rat liver formed deoxyribose phosphate when incubated with hexose diphosphate and threonine it was evident that the threonine aldolase activity of the extracts provided acetaldehyde for the in vitro synthesis of deoxyribose phosphate and it was postulated that this might also occur in vivo ... 

An enzyme found in E. coli converts hexose phosphate to polyol phosphate (XXVIII). Evidence has been found for additional enzjmaes of this type that oxidize phosphate esters of various polyols. 

Phosphate esters of alcohols Glycerophosphate Hexose phosphates Phosphorylcholine... 

From my laboratory and the laboratories of Ef Racker, Frank Dickens and Melvin Calvin, the years that followed witnessed a series of parallel and often highly synergistic discoveries on the nature of the pentose phosphate pathway and the path of carbon in photosynthesis. Andrew Benson and others in Calvin s laboratory, had shown that phosphate esters of ribulose and sedoheptulose were early products of CO2 fixation in photosynthesis,and the immediate precursor of phosphoglyceric acid, and therefore the primary CO2 acceptor, appeared to be ribulose diphosphate. The major problems became (1) to find the enzyme or enzymes that catalyzed the formation of phosphoglyceric acid from ribulose diphosphate and (2) to define the reactions leading to the synthesis of ribulose diphosphate from triose and hexose phosphates. 

We had already shown that sedoheptulose 7-phosphate was an intermediate in the conversion of pentose phosphate to hexosemonophosphate in crude liver extracts, since it accumulated early in the reaction and then disappeared, coincident with the formation of hexose phosphate. The enzyme that catalyzed the interconversion of sedoheptulose 7-phosphate and fructose 6-phosphate was discovered in my laboratory in 1953, and with Paul Marks and Howard Hiatt, we showed that it catalyzed a Cj-transfer from the substrate to a suitable aldehyde donor. This led to the discovery of another new phosphate ester, erythrose 4-phospWe, formed in the Cs-transfer from sedoheptulose 7-phosphate to glyceraldehyde 3-phosphate. Finally, erythrose 4-phosphate could be shown to be the acceptor for a second reaction catalyzed by transketolase, with xylulose 5-phosphate as the donor. All of the steps in the pentose phosphate pathway had now been elucidated (Fig. 2). Erythrose 4-phosphate was also shown to condense with glyceraldehyde 3-phosphate to... 

It had been known from at least the time of Pasteur that the presence of sodium or potassium phosphate aided the progress of a yeast fermentation. Later intensive study showed that a complex group of enzymes (phosphatases and phosphorylases) was responsible for the phosphorylation, dephosphorylation and interconversion of D-glucose 6-phosphate, D-fructose 6-phosphate, D-fructose 1,6-diphosphate and similar substances in various types of cells and muscle tissue. Detailed reviews of the field are available. - A further advance was made in 1936, when Cori and Cori noted that in certain circumstances well-washed frog muscle immersed in a sodium phosphate buffer utilized the inorganic phosphate to produce a new hexose phosphate (the Cori ester). This compound was later shown to be a-D-glucopyranose-l-phosphate and yielded crystalline dipotassium and brucine salts. The Cori ester arose because... 

Sugar phosphates, mainly the hexose mono- and di-phosphates, play an important part in alcoholic fermentation. The calcium salts of these esters have been prepared. 

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