Hydroxypyruvic acid phosphate

The specificity of purified transketolase is rather broad, and several compounds have been shown (93) to act as donors of active glycolaldehyde. Included in these compounds are D-ribulose 5-phosphate, D-sedoheptulose 7-phosphate, D-fructose 6-phosphate, L-erythrulose, and hydroxypyruvic acid. A number of aldehydes have been shown to act as active glycolalde-... 

Transketolase (TKase) [EC 2.2.1.1] essentially catalyzes the transfer of C-2 unit from D-xylulose-5-phosphate to ribose-5-phosphate to give D-sedoheptulose-7-phosphate, via a thiazolium intermediate as shown in Fig. 16. An important discovery was that hydroxypyruvate works as the donor substrate and the reaction proceeds irreversibly via a loss of carbon dioxide (Fig. 17). In this chapter, we put emphasis on the synthesis with hydroxypyruvate, as it is the typical TPP-mediated decarboxylation reaction of a-keto acid. ... 

While formic acid accumulation in folic deficiency makes it clear that the main route for formate removal is folic-mediated, little is known in this respect about formaldehyde, which arises from the oxidation of methyl groups or the folic-mediated reduction of formate (Section II, 5). Perhaps an important connection between Ci and the principal pathways for substrates is indicated by the finding that HCHO is an excellent acceptor for the ketol group ( active glycolaldehyde ) formed from a variety of ketose phosphates and from hydroxypyruvate (Dickens and Williamson, 1958). This reaction may be formulated as follows ... 

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