In vivo phosphorylation of sorghum leaf phosphoenolpyruvate carboxylase.

The use of immunological techniques allowed us to purify close to homogeneity phosphoenolpyruvate carboxylase (PEPc, EC 4.1.1.31) from sorghum leaf. It was thus established that: 1) this protein is phosphorylated in vivo on seryl residues; 2) in C4-type photosynthesis, the phosphorylation process mainly concerns the PEPC isozyme form G; 3) enzyme phosphorylation displays significant variations through a day-night alternation which therefore suggests light control of the process.