Catalytic properties and substrate specificity of 3-hexulose phosphate synthase fromMethylomonas M15

Summary 3-Hexulose phosphate synthase was purified in 94% yield from Methylomonas M15. The enzyme did not form a Schiff-base intermediate with d-ribulose 5-phosphate that could be reduced by NaBH₄. However, the enzyme required Mg²⁺ or Mn²⁺ ions for activity and was inactivated in the presence of EDTA. The latter is a property of class II aldolases. The enzyme accepted a wide range of other aldehydes in addition to its natural substrate formaldehyde, while d-ribulose 5-phosphate could not be replaced. This makes it an attractive tool for the synthesis of higher sugar phosphates.Offprint requests to: M.-R. Kula