[Purification and properties of 3-hexulosephosphate synthase from facultative methylotroph Pseudomonas oleovorans]

3-Hexulosephosphate synthase (HPS), the key enzyme of the hexulosephosphate cycle of formaldehyde fixation, was isolated from facultative methylotroph Pseudomonas oleovorans. Enzyme was purified 100-fold. The purification procedure involved fractionation with ammonium sulfate, gel-filtration on Sephadex G-150 and chromatography on DEAE-Sephadex A-50. The purified enzyme gave single band on analytical polyacrylamide gel electrophoresis. Optimal conditions for activity of HPS are: pH 7,0, temperature 50 degrees C. The molecular weight was calculated to be 45 000 from gel-filtration experiments. HPS is active only in the presence of Mg2+ or Mn2+. Ribulose-5-phosphate is the sole acceptor of formaldehyde. Activity of the enzyme is inhibited by NADH and NADPH.