Wide specificity for both reactants, e.g. converts hydroxypyruvate and R-CHO into CO(2) and R-CHOH-CO-CH(2)OH.
Transketolase from Alcaligenes faecalis shows high activity with D-erythrose as acceptor.

Transketolase catalyzes the reversible transfer of a two-carbon ketol unit from xylulose 5-phosphate to an aldose receptor, such as ribose 5-phosphate, to form sedoheptulose 7-phosphate and glyceraldehyde 3- phosphate. This enzyme, together with transaldolase (EC 2.2.1.2), provides a link between the glycolytic and pentose-phosphate pathways.

In most sources where TK has been purified, it is a homodimer of approximately 70 Kd subunits. TK sequences from a variety of eukaryotic and prokaryotic sources show that the enzyme has been evolutionarily conserved.

In the peroxisomes of methylotrophic yeast Hansenula polymorpha, there is a highly related enzyme, dihydroxy-acetone synthase EC 2.2.1.3 (also known as formaldehyde transketolase), which exhibits a very unusual specificity by including formaldehyde amongst its substrates.

It has been selected two regions of TK as signature patterns. The first, located in the N-terminal section, contains a histidine residue which appears to function in proton transfer during catalysis. The second, located in the central section, contains conserved acidic residues that are part of the active cleft and may participate in substrate-binding.
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