D-Xylulose-l-phosphate

FruA was added to the reaction mixture when the oxidation of L-glycerol-3-phos-phate catalyzed by L-GPO was complete. FruA was used for catalyzing the aldol addition of DHAP onto 2-chloro- or 2-bromoacetaldehydes 20 to give the aldol adduct 5-chloro or 5-bromo-D-xylulose-l-phosphate. The yield was quantitative. 

The dephosphorylation of 5-chloro and 5-bromo-D-xylulose-l-phosphate was carried out by the addition of acid phosphatase. After purification, 5-chloro-D-xylu-lose and 5-bromo-D-xylulose were recovered as pure compounds in 47 and 12% yields, respectively, from DHAP. In this study, we have shown that DHAP generated from glycidol 7 can be used in situ as a donor substrate of FruA in the presence of 2-halo-acetaldehydes 20 as acceptor substrates for the synthesis of 5-halo-D-xylulose 19. Given that DHAP aldolases display a broad specificity towards acceptor substrates, this strategy can be applied generally to the synthesis of various analogs of monosaccharides. 

Hoberman, H. D., Adduct formation between hemoglobin and 5-deoxy-D-xylulose-l-phosphate. Biochem. Biophys. Res. Common. 90, 764-768 (1979). 

The major product of the condensation of glycolaldehyde and dihy-droxyacetone phosphate in the presence of aldolase is considered to be D-xylulose-l-phosphate (Fig. 18). 

Glucuronate is reduced to L-gulonate in an NADPH-dependent reaction L-gulonate is the direct precursor of ascorbate in those animals capable of synthesizing this vitamin. In humans and other primates as well as guinea pigs, ascorbic acid cannot be synthesized because of the absence of L-g ulonolactone oxidase. L-Gulonate is metabolized ultimately to D-xylulose 5-phosphate, a constituent of the pentose phosphate pathway. 

D-glyceraldehyde-3-phosphate, pyruvate (G3P) l-deoxy-D-xylulose-5-phosphate (DXP) 2C-methyl-D-erythritol-4-phosphate (MEP) 4-diphosph-2C-methyl-D-erythritol (CDP-ME) 4-diphosphocytidyl-2C-methyl-D-erythritol-2-phophate (CDP-MEP)... 

Sprenger, G.A. et al.. Identification of a thiamin-dependent synthase in Escherichia coli required for the formation of the 1-deoxy-D-xylulose 5-phosphate precursor to isoprenoids, thiamin, and pyridoxol, Proc. Natl. Acad Sci. USA 94, 12857, 1997. Lange, B.M. et al., A family of transketolases that directs isoprenoid biosynthesis via a mevalonate-independent pathway, Proc. Natl. Acad Sci. USA 95, 2100, 1998. Lois, L.M. et al., Cloning and characterization of a gene from Escherichia coli encoding a transketolase-like enzyme that catalyzes the synthesis of D-1- deoxyxylulose 5-phosphate, a common precursor for isoprenoid, thiamin, and pyridoxol biosynthesis, Proc. Natl. Acad. Sci. USA 95, 2105, 1998. 

Lichtenthaler, H.K., The l-deoxy-d-xylulose-5-phosphate pathway of isoprenoid biosynthesis in plants, Anna. Rev. Plant Physiol. Plant Mol. Biol. 50, 47, 1999. 

Lois, L.M. et al.. Carotenoid biosynthesis during tomato fruit development regulatory role of 1-deoxy-D-xylulose 5-phosphate synthase. Plant J. 22, 503, 2000. 

Estevez, J.M. et al., l-Deoxy-D-xylulose-5-phosphate synthase, a limiting enzyme for plastidic isoprenoid biosynthesis in plants, J. Biol. Chem. 276, 22901, 2001. 

This enzyme [EC 5.1.3.4] catalyzes the interconversion of L-ribulose 5-phosphate and D-xylulose 5-phosphate. 

The enzymatic conversion of l-deoxy-D-xylulose-5-phosphate to pyridoxol phosphate (Vitamin B6) in E. coli was demonstrated <99JA7722>. 

Singh N, Cheve G, Avery MA, McCurdy CR (2006) Comparative protein modeling of l-deoxy-D-xylulose-5-phosphate reductoi-somerase enzyme from Plasmodium falciparum a potential target for antimalarial drug discovery. J Chem Inf Model 46(3) 1360-1370... 

Transketolase (TK, EC 2.2.1.1), one of the enzymes in the pentose phosphate pathway, reversibly transfers an active hydroxyaldehyde group from a ketol donor to an a-hydroxyaldehyde acceptor to yield a ketose with the 3(.S ),4( / -configuration 82 TK transfers the C(l)-C(2) ketol unit of D-xylulose 5-phosphate onto D-ribose 5-P and thus generates glyceraldehyde-3-phosphate... 

L-Ribulose-5-phosphate 4-epimerase catalyzes epimerization at the C4 position of L-ribulose-5-phosphate to form D-xylulose-5-phosphate, allowing bacteria to utilize arabi-nose as an energy source in the pentose phosphate pathway ". The enzyme from E. coli is comprised of four equal 25.5 kDa subunits and shows very close resemblance to the... 

R,4S)-3,4-Dihydroxy-5-oxohexylphosphonic acid (282), an isosteric analogue of l-deoxy-D-xylulose-5-phosphate (DXP), the first C5 intermediate in the MEP pathway for isoprenoid biosynthesis has been synthesized from (+)2,3-0-benzylidene-D-threitol (283) by a seven step reaction sequence. This phosphonate (282) was next enzymatically converted into (3R,4R)-3,4,5-trihy-droxyphosphonic acid (284), an isosteric analogue of 2-C-methyl-D-erythritol-4-phosphate (Scheme 72). 

Of the two D-tetroses, only 4-phospho-D-erythrose is found in any quantity, as an intermediate in the photo synthetic reactions. Of the four pentoses, only D-ribose and D-xylose occur to any extent. The phospho- z/J6>-D-pentoses, D-ribose-5-phosphate and D-xylose-5-phosphate, are found in the photo synthetic reactions. Three phospho- t6>-D-pentoses are also found as intermediates in the photosynthetic reactions D-ribulose-5-phosphate, D-xylulose-5-phosphate, and D-ribulose-l,5-bis-phosphate, the latter carbohydrate being directly involved in the fixing of C02in photosynthesis. 

The thiamin biosynthetic pathway is outlined in Fig. 22 [88]. Overall the pathway involves the separate synthesis of the thiazole 111 and the pyrimidine 114 which are then coupled. l-Deoxy-D-xylulose-5-phosphate (see sections 11 and 12 of this review) is the precursor to the five carbon unit of the thiazole [89], cysteine is the sulfur source [90, 91], and the C2-N3 atoms of the thiazole are derived from the a-carbon and the amino group of tyrosine [92-94]. The pyrimidine is derived from 5-aminoimidazole riboside (AIRs), an intermediate on the purine biosynthetic pathway. This reaction involves a complex rearrangement in which the C4 carbon of AIRs is inserted into the C4-C5 imidazole double bond, converting the imidazole to a pyrimidine, and the C2 carbon of AIRs is used to methylate the C2 position of the imidazole [95-98]. 

Figure 4. Effect of pH on the decomposition of D-xylulose-L-cysteine in a boiling 0.5 M aqueous phosphate bvffer.

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. 

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