ATP + D-ribulose 5-phosphate = ADP + D-ribulose 1,5-bisphosphate + H(+) Light regulated via thioredoxin by reversible oxidation/reduction of sulfhydryl/disulfide groups. Carbohydrate biosynthesis; Calvin cycle. On the 2D-gel the determined pI of this protein (spot N148) is: 5.6, its MW is: 37 kDa. Belongs to the phosphoribulokinase family.