Activating Compound | Comment | Organism | Structure |
---|---|---|---|
additional information | active centers of the enzyme are functionally nonequivalent with respect to ribose 5-phosphate binding | Saccharomyces cerevisiae |
KM Value [mM] | KM Value Maximum [mM] | Substrate | Comment | Organism | Structure |
---|---|---|---|---|---|
0.06 | - |
D-ribose 5-phosphate | first active center of transketolase | Saccharomyces cerevisiae | |
0.06 | - |
D-ribose 5-phosphate | pH 7.6, 25°C, affinity to the first active center when the second center is unoccupied | Saccharomyces cerevisiae | |
0.08 | - |
D-ribose 5-phosphate | hemiholotransketolase 2, i.e., transketolase, in which the functional active center has a lower affinity for thiamine diphosphate than hemiholotransketolase 1 | Saccharomyces cerevisiae | |
0.09 | - |
D-ribose 5-phosphate | hemiholotransketolase 1, i. e. transketolase, in which the functional active center has a higher affinity for the coenzyme than the other active center | Saccharomyces cerevisiae | |
0.25 | - |
D-ribose 5-phosphate | second active center of transketolase | Saccharomyces cerevisiae | |
0.25 | - |
D-ribose 5-phosphate | pH 7.6, 25°C, affinity to the second active center when the first center is occupied | Saccharomyces cerevisiae |
Organism | UniProt | Comment | Textmining |
---|---|---|---|
Saccharomyces cerevisiae | - |
- |
- |
Purification (Comment) | Organism |
---|---|
to homogeneity | Saccharomyces cerevisiae |
Renatured (Comment) | Organism |
---|---|
hemiholotransketolase 1 is the enzyme in which the only functional active center is the one exhibiting higher affinity for thiamine diphosphate. In the presence of Ca2+, the active centers of transketolase differ in their affinity for thiamine diphosphate by approximately one order of magnitude. When adding an equimolar amount of thiamine diphosphate to apotransketolase, it becomes completely bound to the 1 active center and is not dissociated from it in the course of subsequent experiments. Hemiholotransketolase 2 is the enzyme in which the only functional active center is the one exhibiting lower affinity for the coenzyme. In order to obtain this species of transketolase, active center 1, the affinity of which for thiamine diphosphate is higher, is to be blocked by an inactive analogue of the coenzyme, hydroxythiamine diphosphate | Saccharomyces cerevisiae |
Specific Activity Minimum [µmol/min/mg] | Specific Activity Maximum [µmol/min/mg] | Comment | Organism |
---|---|---|---|
20 | - |
- |
Saccharomyces cerevisiae |
Storage Stability | Organism |
---|---|
4°C, 50% saturated solution of ammonium sulfate, pH 7.6 | Saccharomyces cerevisiae |
Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
---|---|---|---|---|---|---|
D-xylulose 5-phosphate + D-ribose 5-phosphate | - |
Saccharomyces cerevisiae | sedoheptulose 7-phosphate + D-glyceraldehyde 3-phosphate | - |
? | |
D-xylulose 5-phosphate + D-ribose 5-phosphate | the active centers of the enzyme are nonequivalent with respect to ribose 5-phosphate binding. Under the conditions where only one out of the two active centers of transketolase is functional, their affinities for ribose 5-phosphate are identical. Nonequivalence becomes apparent when the substrate interacts with one of the two active centers. As a consequence, the affinity of the second active center for ribose 5-phosphate decreases | Saccharomyces cerevisiae | sedoheptulose 7-phosphate + D-glyceraldehyde 3-phosphate | - |
? |
Cofactor | Comment | Organism | Structure |
---|---|---|---|
thiamine diphosphate | in the presence of Ca2+, the active centers of transketolase differ in their affinity for thiamine diphosphate by approximately one order of magnitude. Hemiholotransketolase 1 is the enzyme in which the only functional active center is the one exhibiting higher affinity for thiamine diphosphate. When adding an equimolar amount of thiamine diphosphate to apotransketolase, it becomes completely bound to the 1 active center and is not dissociated from it in the course of subsequent experiments. Hemiholotransketolase 2 is the enzyme in which the only functional active center is the one exhibiting lower affinity for the coenzyme. In order to obtain this species of transketolase, active center 1, the affinity of which for thiamine diphosphate is higher, is to be blocked by an inactive analogue of the coenzyme, hydroxythiamine diphosphate | Saccharomyces cerevisiae |