Literature summary for 2.2.1.1 extracted from

Mitschke, L.; Parthier, C.; Schroeder-Tittmann, K.; Coy, J.; Luedtke, S.; Tittmann, K.
The crystal structure of human transketolase and new insights into its mode of action (2010), J. Biol. Chem., 285, 31559-31570.

Cloned(Commentary)

Cloned (Comment)	Organism
expression in Escherichia coli	Homo sapiens

Crystallization (Commentary)

Crystallization (Comment)	Organism
to 1.75 A resolution, space group C2 with one monomer in the asymmetric unit. Two monomers form the homodimeric biological assembly with two identical active sites at the dimer interface. The protomer exhibits the typical three alpha/beta-domain structure and topology reported for transketolases from other species, with structural differences for several loop regions and the linker that connects the diphosphate and pyridine domain. Two lysines and a serine interact with the beta-phosphate of thiamine diphosphate. Residue Gln189 spans over the thiazolium moiety of thiamine diphosphate and replaces an isoleucine found in most non-mammalian transketolases. The side chain of Gln428 forms a hydrogen bond with the 4-amino group of thiamine diphosphate and replaces a histidine that is invariant in all nonmammalian transketolases. All other amino acids involved in substrate binding and catalysis are strictly conserved. Formation of the central 1,2-dihydroxyethyl-thiamine diphosphate carbanion-enamine intermediate is thermodynamically favored with increasing carbon chain length of the donor ketose substrate	Homo sapiens

Crystallization (Comment)

Organism

to 1.75 A resolution, space group C2 with one monomer in the asymmetric unit. Two monomers form the homodimeric biological assembly with two identical active sites at the dimer interface. The protomer exhibits the typical three alpha/beta-domain structure and topology reported for transketolases from other species, with structural differences for several loop regions and the linker that connects the diphosphate and pyridine domain. Two lysines and a serine interact with the beta-phosphate of thiamine diphosphate. Residue Gln189 spans over the thiazolium moiety of thiamine diphosphate and replaces an isoleucine found in most non-mammalian transketolases. The side chain of Gln428 forms a hydrogen bond with the 4-amino group of thiamine diphosphate and replaces a histidine that is invariant in all nonmammalian transketolases. All other amino acids involved in substrate binding and catalysis are strictly conserved. Formation of the central 1,2-dihydroxyethyl-thiamine diphosphate carbanion-enamine intermediate is thermodynamically favored with increasing carbon chain length of the donor ketose substrate

Homo sapiens

KM Value [mM]

KM Value [mM]	KM Value Maximum [mM]	Substrate	Comment	Organism
0.255	-	D-xylulose 5-phosphate	recombinant enzyme, pH 7.6, 30°C	Homo sapiens
0.303	-	D-xylulose 5-phosphate	His-tagged recombinant enzyme, pH 7.6, 30°C	Homo sapiens
0.48	-	D-ribose 5-phosphate	recombinant enzyme, pH 7.6, 30°C	Homo sapiens
0.61	-	D-ribose 5-phosphate	His-tagged recombinant enzyme, pH 7.6, 30°C	Homo sapiens

Organism

Organism	UniProt	Comment	Textmining
Homo sapiens	P29401	-	-

Reaction

Reaction	Comment	Organism	Reaction ID
sedoheptulose 7-phosphate + D-glyceraldehyde 3-phosphate = D-ribose 5-phosphate + D-xylulose 5-phosphate	formation of the central 1,2-dihydroxyethyl-thiamine diphosphate carbanion-enamine intermediate is thermodynamically favored with increasing carbon chain length of the donor ketose substrate	Homo sapiens	a

Specific Activity [micromol/min/mg]

Specific Activity Minimum [µmol/min/mg]	Specific Activity Maximum [µmol/min/mg]	Comment	Organism
2.7	-	His-tagged recombinant enzyme, pH 7.6, 30°C	Homo sapiens
5.5	-	recombinant enzyme, pH 7.6, 30°C	Homo sapiens

Substrates and Products (Substrate)

Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.	Reac.
D-xylulose 5-phosphate + D-ribose 5-phosphate	-	Homo sapiens	sedoheptulose 7-phosphate + D-glyceraldehyde 3-phosphate	-	?

Synonyms

Synonyms	Comment	Organism
TKT	-	Homo sapiens

Turnover Number [1/s]

Turnover Number Minimum [1/s]	Turnover Number Maximum [1/s]	Substrate	Comment	Organism	Structure
3.1	-	D-xylulose 5-phosphate	His-tagged recombinant enzyme, pH 7.6, 30°C	Homo sapiens
6.3	-	D-xylulose 5-phosphate	recombinant enzyme, pH 7.6, 30°C	Homo sapiens

Cofactor

Cofactor	Comment	Organism	Structure
thiamine diphosphate	two lysine residues and a serine interact with the beta-phosphate of thiamine diphosphate. Residue Gln189 spans over the thiazolium moiety of thiamine diphosphate	Homo sapiens