Enzymatic Formation of a New Monosaccharide, 1-Deoxy-D-altro- heptulose Phosphate, from DL-Acetoin and D-Ribose 5-Phosphate by a Transketolase Mutant of Bacillus pumilus

Abstract

1-Deoxy-D-altro-heptulose phosphate (DAHP) synthase activity was found in the cell-free extract of a transketolase mutant, BG2532, of Bacillus pumilus IFO 12089. The enzyme was partially purified by protamine sulfate treatment, ammoniumsulfate fractionation, DEAEcellulose and hydroxylapatite column chromatography. When DL-acetoin and D-ribose 5-phosphate were incubated with the partially purified enzyme preparation, DAHP and acetaldehyde were detected as reaction products. Thiamine pyrophosphate (TPP) and Mg²⁺ were required as co factors. The results of the stoichiometric measurementsindicate that DAHPsynthesis proceeds according to the following formula :
TPP5Mg²⁺
DL-Acetoin+D-Ribose 5-phosphate → Acetaldehyde+DAHP
Intracellular DAHP formed by this reaction may be excreted and accumulated in culture broth as 1-deoxy-D-altro-heptulose after dephosphorylation.