Aldoses ketoses

Over 200 different monosaccharides are known They can be grouped according to the number of carbon atoms they contain and whether they are polyhydroxy aide hydes or polyhydroxy ketones Monosaccharides that are polyhydroxy aldehydes are called aldoses, those that are polyhydroxy ketones are ketoses Aldoses and ketoses are further classified according to the number of carbon atoms m the mam chain Table 25 1 lists the terms applied to monosaccharides having four to eight carbon atoms... 

Dimedone reacts with carbonyl compounds with the elimination of water yielding the condensation product [1]. The reaction is specific for ketoses aldoses do not react or only weakly [6],... 

Experiment Substrate thioketose (mm) Glcl (units) Process Reaction time (days) Ketose/aldose... 

Xylose isomerases with higher thermostability were found in the strains of Streptomyces and relaxed Actinoplanaceae (which includes the generdLAmpullariella and Actinopianes). High thermo-tolerance is desirable for production of HFCS because at equilibrium, as the temperature of the enzyme reaction is increased, the ketose/aldose ratio increases proportionately 30). In addition, reactors running at higher temperatures have less risk of microbial contamination, allowing for less frequent and less costly enzyme replacement. 

Ketose-aldose isomerases catalyze the interconversion of aldose and ketose in sugar metabolism. Owing to their value in the sngar industry for the preparation of high-fructose... 

PMI from the fungus Candida albicans is a metalloenzyme of 48.7 kDa, which catalyzes the interconversion of phosphofructose and phosphomannose. The structure of this enzyme is different from that of rabbit PGI (with an a// -fold and not a metalloenzyme) and those of the few metallo-(phospho-)ketose/aldose isomerases discussed in... 

Scheme 11. Tandem enzymatic chain extension catalyzed by transketolase, aided by the combination with a suitable ketose-aldose isomerase...

The Lobry de Bruyn-Alberda van Ekenstein transformation is the basic mechanism for a better miderstanding of the relationship between ketoses, aldoses, and the degradation products thereof [such as the saccharinic acids, 5-(hydroxymethyl)-2-furaldehyde, and the 3-deoxyglycosuloses]. ... 

Ketose-aldose pairs of sugars frequently are named by inserting the letters uf in the name of the corresponding aldose to derive the name of the ketose. An example is erythrose - erythrulose. 

Triose phosphate isomerase (TPI) catalyzes the ketose-aldose isomerism between glyceraldehyde 3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP) during glycolysis. The rate-determining step for the reaction is product dissociation. 

Although advantageous for the identification of the sugars, the phenyl osazones are not applicable to the isolation of sugars. The phenylhydrazine groups are removed by treatment with benzaldehyde, concentrated hydrochloric acid, or particularly well by pyruvic acid (230), but the resulting product, a sugar osone, is a mixed ketose-aldose. 

The suffix -ose is used to signify a carbohydrate. Hundreds of diflFerent monosaccharides are known, each of which can generally be classified as either an aldose or a ketose. Aldoses contain an aldehyde moiety, while ketoses contain a ketone moiety. According to this classification scheme, glucose is an aldose and fiructose is a ketose. 

The successful apphcation of the classical two-step fermentation process showed that the combination of dehydrogenases, that is, SLDH, SDH, and SNDH, was efficient to sequentially convert D-sorbitol to 2-KLG, which was the direct precursor of l-AA [32, 33]. Therefore, the most straightforward idea was to integrate the three ketose/aldose dehydrogenases into one microorganism. Therefore, the first thing was to identify these ketose/aldose dehydrogenases. 

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