InterPro domain: IPR006082

Phosphoribulokinase (PRK) 2.7.1.19 catalyses the ATP-dependent phosphorylation of ribulose-5-phosphate to ribulose-1,5-phosphate, a key step in the pentose phosphate pathway where carbon dioxide is assimilated by autotrophic organisms [ 1 ]. In general, plant enzymes are light-activated by the thioredoxin/ferredoxin system, while those from photosynthetic bacteria are regulated by a system that has an absolute requirement for NADH. Thioredoxin/ferredoxin regulation is mediated by the reversibleoxidation/reduction of sulphydryl and disulphide groups. In the spinach enzyme ( P09559 ) the participating residues are Cys-16 and Cys-55. Sequence analysis shows the first of these cysteines to be present in the ATP-binding site [ 2 ]; neither is found in the bacterial sequences.

1. The form II fructose 1,6-bisphosphatase and phosphoribulokinase genes form part of a large operon in Rhodobacter sphaeroides: primary structure and insertional mutagenesis analysis. Biochemistry 29, 8085-93
2. Characterization of the regulatory thioredoxin site of phosphoribulokinase. J. Biol. Chem. 263, 123-9