Yeast transketolase

Effenberger, F., NuU, V. and Ziegler, T., Preparation of optically pure 1-2-hydroxyaldehydes with yeast transketolase. Tetrahedron Lett., 1992, 33, 5157. 

Attempts to crystallize DXS with the aim of determining the enzyme s 3D structure have failed so far. In the absence of a 3D structure, yeast transketolase structure was used as a model for DXS. Amino acid residues which are conserved... 

Structural studies with yeast transketolase a) M. Sundstrom, Y. Lindqvist, G. Schneider, FEES Lett. 1992, 313, 229-251 b) Y. Lindqvist, G. Schneider, U. Ermler, M. Sundstrom,... 

Mostly the baker s yeast transketolase has been used so far to prepare several valuable ketose sugars and derivatives 141 (cf. Sect. 7). Recently, the transketolase was utilized in the key stereogenic transformation of racemic 2-hydroxybutyraldehyde 142 into the homochiral synthon 5,6-dideoxy-D-t/ireo-hexulose 110 for the chemoenzymatic synthesis of (+ )-exo-brevicomin 107 [314], Transketolase has also been applied for the in-situ generation of Ery4P (35) from Fru6P (38) in a multi-enzymatic synthesis of 34 (Scheme 5). 

Effenberger and coworkers reported a de novo approach to 5-thio-D-f/zreo-2-pentulofuranose (5-thio-D-xylulose, 20) (Figure 9.7) from 2-mercaptoacetaldehyde, employing rabbit muscle aldolase (RAMA EC 4.1.2.13) and yeast transketolase (EC 2.2.1.1) as the catalysts [32]. 

Konig, S., Schellenberger, A., Neee, H., Schneider, G. (1994), Specificity of coenzyme binding in thiamin diphosphate-dependent enzymes. Crystal structures of yeast transketolase in complex with analogs of thiamin diphosphate, J. Biol. Chem. 269, 10879-10882. 

New sources of 254 include Angylocalyx pynaertii [581], Morus bombycis [563], and M. alba [582]. A recent synthesis of fagomine was based on the yeast transketolase-catalyzed reaction of 3-hydroxy-4-oxobutyronitrile with lithium hydroxypyruvate [583]. 

Benaissi K, Helaine V, Prevot V, Forano C, Hecquet L. Efficient immobilization of yeast transketolase on layered double hydroxides and application for ketose synthesis. Adv. Synth. Catal 2011 353 1497-1509. 

Yeast transketolase 3 of the 18 Trp-residues have been modified, leading to a decrease in Km 167)... 

An impediment to a wider use of transketolases, however, was the lack of the catalyst itself, which had to be tediously purified from sources such as baker s yeast or spinach leaves [4]. With the advent of recombinant DNA technologies. 

Aldehydes lacking an OH group at C2 are also transformed by transketolase, leading to a 3S configuration of the hydroxyl group in the deoxyketose product [7a, 9] albeit with a significantly lower rate than with the hydroxylated acceptors [6b, 10. In contrast to the transketolases from spinach and yeast [9, no conversion of aromatic aldehydes, e.g., benzaldehyde or hydroxybenzaldehydes, could be detected with purified E. coli transketolase [6b]. 

For synthetic purposes the E. coli transketolase has a certain advantage over the enzymes from spinach and yeast, because the conversion of a-hydroxypyru-vate with a rate of 60 U (mg of protein) [6b] is significantly higher than the rates of 2 U mg" and 9 U mg reported for the spinach and yeast enzymes [9, 11],... 

By 1998, X-ray structures had been determined for four thiamin diphosphate-dependent enzymes (1) a bacterial pyruvate oxidase,119120 (2) yeast and bacterial pyruvate decarboxylases,121 122c (3) transketolase,110123124 and (4) benzoylformate decarboxylase.1243 Tire reactions catalyzed by these enzymes are all quite different, as are the sequences of the proteins. However, the thiamin diphosphate is bound in a similar way in all of them. 

Because of its ready availability and stability, the transketolase from yeast has been studied more frequently than enzymes from other sources for mechanistic as well as synthetic purposes. A valuable feature is that during the first round of a ping-pong catalytic cycle the natural ketose donor component(s) can... 

Transketolase from common yeast (Saccharomyces cerevisiae) is commercially available, but it is possible to work with a partially purified enzyme, isolated with little expense from spinach leaves.54 Transketolase catalyzes the transfer of a hydroxyacetyl group, reversibly from a ketose phosphate, or irreversibly from hydroxypyruvate to an acceptor aldose, phosphorylated or not.55 It requires thiamine pyrophosphate as a coenzyme, but only in catalytic amounts. In all the cases listed in Table V, the new chiral center, C-3 of the ketose, has the l-glycero configuration. 

B.H. Robinson and K. Chun. 1993. The relationships bet veen transketolase, yeast pyruvate decarboxylase and pyruvate dehydrogenase of the pyruvate dehydrogenase complex FEBS Lett. 328 99-102. (PubMed)... 

The first stage, involving the transfer of active glycolaldehyde, can be accomplished in the laboratory by use of spinach or rat-liver transketolase, and the products isolated and characterized as the barium salt and 2,7-anhydride, respectively. The second stage is catalyzed by liver or yeast transaldolase and is believed to involve the enzymic transfer of a 1,3-di-hydroxy-2-propanone residue sedoheptulose 7-phosphate and D-fructose... 

Thiamine derivatives inhibit glucose synthesis, transketolase (yeast), phosphodiesterase (snake venom), thiamine triphosphatase, thymidylate kinase. 

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