Abstract
The enzyme obtained from a cell-free extract of baker's yeast is able to form thiamine diphosphate (TDP) from thiamine monophosphate (TMP) with ATP and Mg^<2+> as well as from thiamine. The enzyme which synthesize TDP from TMP was purified with heat treatment. ammonium sulfate fractionation and DEAE-cellulose column chromatography. The obtained enzyme was partially purified 18 fold in a specific activity of TDP formation from TMP, accompanying the thiaminokinase activity which was not able to separate and also containing a little TMPase activity. In order to exclude the participation of TMPase in TDP formation from TMP, a chemically synthesized TMP-^<32>P was used as a substrate and TDP-^<32>P formed enzymatically was isolated from the reaction mixture. The consistency of specific radio-activities of the TMP-^<32>P used and the formed TDP-^<32>P suggests the direct phosphorylation of TMP to form TDP, that is an exsistence of TMP-phosphokinase.
