Bifunctional serine/threonine kinase and phosphorylase involved in the dark/light-mediated regulation of PPDK by catalyzing its phosphorylation/dephosphorylation. Dark/light-induced changes in stromal concentrations of the competing ADP and Pi substrates govern the direction of the reaction. In the dark, phosphorylates the catalytic intermediate of PPDK (PPDK-HisP), inactivating it. Light exposure induces the phosphorolysis reaction that reactivates PPDK. Unlike the kinase function which can utilize either Thr or Ser as target, the phosphorylase function has a strict substrate requirement for threonyl phosphate. ADP + N(tele)-phospho-L-histidyl/L-threonyl-[pyruvate, phosphate dikinase] = AMP + H(+) + N(tele)-phospho-L-histidyl/O-phospho-L-threonyl-[pyruvate, phosphate dikinase] H(+) + N(tele)-phospho-L-histidyl/O-phospho-L-threonyl-[pyruvate, phosphate dikinase] + phosphate = diphosphate + N(tele)-phospho-L-histidyl/L-threonyl-[pyruvate, phosphate dikinase] Regulated by light/dark exposure. Interacts with PPDK1. Expressed in green tissues. The initial 51 amino acids are sufficient to act as a chloroplast transit peptide and the removal of the next 35 amino acids reduces the strength of interaction with PPDK significantly, which suggested that these residues are important for binding RP1 and may not be part of the transit peptide (PubMed:21883547). Belongs to the pyruvate, phosphate/water dikinase regulatory protein family. PDRP subfamily.