PTHR43522

TRANSKETOLASE

PANTHER entry
Member databasePANTHER
PANTHER typefamily

Description
Imported from IPR033247

Transketolase
2.2.1.1
(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
[1, 3]
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)
2.2.1.3
(also known as formaldehyde transketolase), which exhibits a very unusual specificity by including formaldehyde amongst its substrates.

1-deoxyxylulose-5-phosphate synthase (DXP synthase)
[2]
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
[4]
. This entry represents the central section there are conserved acidic residues that are part of the active cleft and may participate in substrate-binding
[4]
. This group of proteins includes transketolase enzymes
2.2.1.1
and 2-oxoisovalerate dehydrogenase beta subunit
P37941
1.2.4.4
. Both these enzymes utilise thiamine pyrophosphate as a cofactor, suggesting there may be common aspects in their mechanism of catalysis.

References
Imported from IPR033247

1.Nucleotide and predicted amino acid sequence of a cDNA clone encoding part of human transketolase. Abedinia M, Layfield R, Jones SM, Nixon PF, Mattick JS. Biochem. Biophys. Res. Commun. 183, 1159-66, (1992). View articlePMID: 1567394

2.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. Sprenger GA, Schorken U, Wiegert T, Grolle S, de Graaf AA, Taylor SV, Begley TP, Bringer-Meyer S, Sahm H. Proc. Natl. Acad. Sci. U.S.A. 94, 12857-62, (1997). View articlePMID: 9371765

3.DNA sequence of the yeast transketolase gene. Fletcher TS, Kwee IL, Nakada T, Largman C, Martin BM. Biochemistry 31, 1892-6, (1992). View articlePMID: 1737042

4.Three-dimensional structure of transketolase, a thiamine diphosphate dependent enzyme, at 2.5 A resolution. Lindqvist Y, Schneider G, Ermler U, Sundstrom M. EMBO J. 11, 2373-9, (1992). View articlePMID: 1628611

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