| Description | Transketolase (TK) catalyses 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, provides a link between the glycolytic and pentose-phosphate pathways. TK requires thiamine pyrophosphate as a cofactor. 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 Pichia angusta (Yeast) (Hansenula polymorpha), there is a highly related enzyme, dihydroxy-acetone synthase (DHAS) (also known as formaldehyde transketolase), which exhibits a very unusual specificity by including formaldehyde amongst its substrates. 1-deoxyxylulose-5-phosphate synthase (DXP synthase) [ ] is an enzyme so far found in bacteria (gene dxs) and plants (gene CLA1) which catalyses the thiamine pyrophosphoate-dependent acyloin condensation reaction between carbon atoms 2 and 3 of pyruvate and glyceraldehyde 3-phosphate to yield 1-deoxy-D-xylulose-5-phosphate (dxp), a precursor in the biosynthetic pathway to isoprenoids, thiamine (vitamin B1), and pyridoxol (vitamin B6). DXP synthase is evolutionary related to TK. The N-terminal section, contains a histidine residue which appears to function in proton transfer during catalysis []. This entry represents the central section there are conserved acidic residues that are part of the active cleft and may participate in substrate-binding []. This group of proteins includes transketolase enzymes and 2-oxoisovalerate dehydrogenase beta subunit . Both these enzymes utilise thiamine pyrophosphate as a cofactor, suggesting there may be common aspects in their mechanism of catalysis. This entry conserved acidic residues that are located in the central section, which may participate in substrate-binding [ ]. | Name | Transketolase binding site |
| Short Name | Transketolase_BS | Type | Binding_site |
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