Reversible light activation of the phosphoenolpyruvate carboxylase protein-serine kinase in maize leaves.
C4-leaf phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) undergoes reversible, light-induced increases in its activity-seryl phosphorylation-status in vivo. We now report that the PEPC-protein kinase activity in desalted crude extracts of light-adapted maize leaves is several-fold greater than that from the corresponding dark tissue when in vitro phosphorylation assays are performed with either endogenous or purified dark-form maize PEPC as substrate, both in the absence or presence of okadaic acid, a potent inhibitor of the PEPC type 2A protein phosphatase(s). These and related results indicate that the PEPC protein-serine kinase(s) per se is reversibly light activated in vivo by either covalent modification, protein turnover or, less likely, a tight-binding effector.
Echevarría
C
C
Department of Biochemistry, University of Nebraska-Lincoln 68583-0718.
Vidal
J
J
Jiao
J A
JA
Chollet
R
R
D004789:Enzyme Activation / Q000528:radiation effects; D004988:Ethers, Cyclic / Q000494:pharmacology; D008027:Light; D019319:Okadaic Acid; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D003313:Zea mays / Q000201:enzymology*
D004988:Ethers, Cyclic; D019319:Okadaic Acid; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D010730:Phosphoenolpyruvate Carboxylase