Production and properties of recombinant C3-type phosphoenolpyruvate carboxylase from Sorghum vulgare: in vitro phosphorylation by leaf and root PyrPC protein serine kinases.

In this work, the C3-type form of Sorghum phosphoenolpyruvate carboxylase (PyrPC) was produced in PyrPC-deficient strains of Escherichia coli transformed by a plasmid bearing the corresponding full-length cDNA (CPR1). The full-sized protein was purified to homogeneity by immunoaffinity chromatography. Some functional and regulatory properties were described; notably, the immunopurified PyrPC could be phosphorylated in reconstituted assay by 1) both a mammalian PKA and the PyrPC protein serine kinase purified from Sorghum leaves and 2) a novel protein kinase affinity-purified from Sorghum roots. In all cases phosphorylation was accompanied by a marked reduction in its malate sensitivity.