Xylulose, structure

Complex xylulose structures can also be synthesized by RAMA1741. Employing a one-pot, three-enzyme system with RAMA, triose phosphate isomerase, and l-deoxy-D-xylulose-5-phosphate synthase, l-deoxy-D-xylulose-5-phosphate could be obtained in 47 % yield[75]. Furthermore, a four-enzyme, one-pot system employing FDP-aldolase from S. camosus furnished 5-deoxy-5-ethyl-D-xylulose1761. 

In contrast, much information is available about five-carbon sugars. The most widely studied D-pentoses, D-ribose and 2-deoxy-D-erythro-pentose, are discussed in Section VII (see p. 86). The aldopentoses can form either furanose or pyranose rings, and both structures are known, although not in the same crystal. Crystallographic data have not been obtained for either of the 2-pentuloses D-erythro- and D-threo-2-pentulose ( D-ribulose and D-xylulose ), as they are syrupy. 

Details of these reactions, showing the structures of the molecules involved, are given in Fig. 1. These reactions require xylulose 5-phosphate as well as ribose-5-phosphate. Xylulose 5-phosphate is an epimer (see Topic Jl) of ribulose 5-phosphate and is made by phosphopentose epimerase ... 

Deoxy-D-xylulose is a known natural product. It was first isolated from the fermentation broth of a Streptomyces and later shown to be a precursor of pyridoxol. Its structure can be deduced biogenetically from pyruvate and glyceraldehyde phosphate (Figs. 2 and 3). Two H-labeled DX isotopomers were synthesized chemically. They were incorporated efficiently into the prenyl chains of ubiquinone and menaquinone by wild-type E. coli, indicating that a DX derivative is an isoprenoid precursor (2, 3). 

Carbone V, Ishikura S, Hara A et al (2005) Structure-based discovery of human L-xylulose reductase inhibitors from database screening and molecular docking. Bioorg Med Chem... 

D-Xylose isomerase catalyzes the interconversion between D-xylose and D-xylulose (Fig. 17-21). Since this enzyme acts on D-glucose to produce D-fructose, it is often referred to as glucose isomerase (Fig. 17-21). The isomerization of glucose to fructose by this enzyme is a very important process for the industrial production of high fructose com syrup. This enzyme is also applicable to the synthesis of many aldoses and ketoses because of its wide substrate specificity. The enzyme gene has been cloned from various microorganisms, and the enzyme has been overexpressed, purified, and characterized. Their three dimensional structures have also been determined I203-206. ... 

There are fewer ketoses than there are aldoses because ketoses have one less chiral carbon. The most prevalent of the ketoses are dihydroxyacetone, ribu-lose, xylulose, and fructose (see Figure 4). All four of these sugars are important intermediates in metabolism. Fructose is, along with glucose, part of sucrose or table sugar. Fructose is a ketohexose, and the only one of the four ketoses that can assume a ring structure. Like ribose, fructose forms a five-membered (or furanose) ring and has a and j8 anomers. 

Three structural genes are located in the arabinose operon—araS, araA, and araD. They encode enzymes that convert arabinose to xylulose-5-phosphate. 

Borate is able to complex, via the above mechanism, more readily with the open-chain structure of xylulose as compared to the cyclic hemiacetal form of xylose [44]. This binding preference leads to a shift in the xylose/xylulose isomerization equilibrium in favor of xylulose formation. 

Figure 7.5 Screenshot of the online ARM Database. A list of all logically possible pathw ays from GIyceraldehyde-3-phosphate to Xylulose-5-phosphate is shown. Selection one of the pathways from the list will display the corresponding metabolite structure and conserved carbon atoms in that pathway.

Yeh, J.I. et al (2002) Multistate binding in pyridoxine 5 -phosphate synthase 1.96 A crystal structure in complex with 1-deoxy-D-xylulose phosphate. Biochemistry, 41 (39), 11649-11657. 

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