Purification and properties of thiaminephosphate pyrophosphorylase of Escherichia coli

Thiaminephosphate pyrophosphorylase (EC 2.5.1.3) in Escherichia coli has been purified 175-fold by conventional methods of enzyme purification. General properties of the partially purified enzyme were similar to those of the yeast enzyme except for a small molecular weight of 17,000. The E. coli enzyme was inhibited by a variety of high-energy phosphate compounds. Acetyl phosphate was the most potent inhibitor and resulted in 50% inhibition at 0.5 mm concentration. ATP and acetyl phosphate were both uncompetitive inhibitors with respect to both substrates. Low-energy phosphate compounds and pyridine nucleotides were not able to inhibit the activity. These results, together with the other results obtained, indicate that these high-energy phosphate compounds did not inhibit the enzyme activity after conversion to a common compound. The physiological significance of this type of inhibition was discussed from the point of cellular energy charge.