The activities of pyruvate and 2-oxoglutarate dehydrogenases were determined by a spectrophotometric method according to Massey, that of transketolase deter mined by Racker's method. The values of enzyme activity as well as the thiamine contents in the preparations were compared with those of the animals whose deficiencies were restored by thiamine administration. The thiamine deprivation resul...

For detailed studies on the mode of action of an enzyme a readily available source and a convenient method of preparation are of distinct advantage. Accessible sources such as bakers’ yeast (1) and spinach leaves (2) have, therefore, been used for large-scale preparations of transketolase in spite of the fact that extracts of Escherichia coli, in which the cleavage of ribose-5-P to triose-P was...

For detailed studies on the mode of action of an enzyme a readily available source and a convenient method of preparation are of distinct advantage. Accessible sources such as bakers’ yeast (1) and spinach leaves (2) have, therefore, been used for large-scale preparations of transketolase in spite of the fact that extracts of Escherichia coli, in which the cleavage of ribose-5-P to triose-P was...

We describe a new and better method for determining transketolase (EC 2.2.1.1) activity in human erythrocytes. Heating the hemolysate (55 degrees C, 5 min) inactivates transaldolase (EC 2.2.1.2), the enzyme that catalyzes the formation of fructose 6-phosphate and erythrose 4-phosphate from sedoheptulose 7-phosphate and glyceraldehyde 3-phosphate. The net effect is that the quantity of sedoheptu...

Transketolase, the most critical enzyme of the non-oxidative branch of the pentose phosphate pathway, has been reported as a novel target in Plasmodium falciparum as it has least homology with the human host. Homology model of P. falciparum transketolase (PfTk) was constructed using the crystal structure of S. cervisiae transketolase as a template, and used for the identification and prioritiza...

The enzyme transketolase (Enzyme Commission number: 2.2.1.1) has significant potential as a biocatalyst in the production of pharmaceuticals and fine chemicals. The enzyme catalyses the irreversible transfer of a C2 (1,2dihydroxyethyl) moiety from p-hydroxypyruvate (P-HPA) to a wide range of acceptor substrates in a stereospecific reaction. However, commercial application of transketolase is cu...

Patients with chronic uremia develop neurologic defects which are similar to the demyelinating lesions seen in thiamine deficiency. The present study describes inhibitory effects of uremic material on nervous tissue transketolase, a thiamine-dependent enzyme of the pentose phosphate pathway which has been reported to have functional importance in the metabolism of myelinated nervous structures....

We describe optimized, ultraviolet spectrophotometric procedures for determination of erythrocyte transketolase, glutathione reductase, and aspartate aminotransferase activity, and their activation by their respective coenzymes--thiamine pyrophosphate, flavin-adenine dinucleotide, and pyridoxal-5-phosphate--as tests for vitamin B1, B2, and B6 deficiency. With these procedures we have investigat...

The calcium binding sites of Bakers' Yeast Transketolase (TK) was elucidated by estimating the pKa values of the functional groups that bind to calcium. These pKa's were found to be 6.25 and 7.2 relating to the pKa's of the two immidazol moieties of histidine residues on the enzyme. The rate of the binding of calcium to the enzyme was obtained separately as a function of pH. Maximum values ...

The glaucocystophyte Cyanophora paradoxa is an obligatorily photoautotrophic biflagellated protist containing cyanelles, peculiar plastids surrounded by a peptidoglycan layer between their inner and outer envelope membranes. Although the 136-kb cyanelle genome surpasses higher plant chloroplast genomes in coding capacity by about 50 protein genes, these primitive plastids still have to import >...