The inhibition of ribulose 1,5-bisphosphate carboxylase oxygenase by several 2-carboxyhexitol 1- and 6-phosphates

Abstract

The condensation of D-fructose 6-phosphate or 1-phosphate with cyanide has been used to synthesize 2-carboxyhexitol 6-phosphates and 1-phosphates. The products have been characterized in terms of their action on ribulose bisphosphate carboxylase/oxygenase. The reaction of D-fructose 6-phosphate with cyanide is four times as fast (at 22°C) at pH 7.5 than at pH 11.5 and the primary products of condensation are more easily isolated by anion exchange chromatography. Two minor chromatographic peaks (I and II) for diastereomeric 2-carboxyhexitol 6-phosphates are isolated in addition to two major peaks, III and IV, which are lactones. The lactones are those of 2-C-carboxy-D-glucitol 6-phosphate (CG6P) in peak III and 2-C-carboxy-D-mannitol 6-phosphate (CM6P) in peak IV, as established after dephosphorylation by the relative rates of oxidation by periodate and by gas chromatographic retention times of the acetates. Analogous methodology has been used to synthesize the diastereomeric 2-carboxy-hexitol 1-phosphates (CG1P and CM1P) and their lactones from D-fructose 1-phosphate. The four carboxylates inhibit ribulose bisphosphate carboxylase/oxygenase from spinach or Pseudomonas oxalaticus in the following decreasing order of potency: CG6P, CM6P, CG1P, CM1P. The inhibition pattern suggests that the binding of the 5-phosphate moiety of the intermediate in the reaction catalyzed by ribulose bisphosphate carboxylase/oxygenase may be stronger by an order of magnitude than the binding of the 1-phosphate group.