title: Regulation of C4 photosynthesis: identification of a catalytically important histidine residue and its role in the regulation of pyruvate,Pi dikinase.
abstract: These studies provide further information regarding the mechanism of the light/dark-mediated regulation of pyruvate,Pi dikinase in leaves. It is shown that a catalysis-linked phosphorylation of pyruvate,Pi dikinase can be demonstrated following incubation of the enzyme with [32P]phosphoenolpyruvate or [beta-32P]ATP plus Pi, that the enzyme-bound phosphate is located on a histidine residue, and that this phosphate is retained during ADP-mediated inactivation. Further evidence is provided that phosphorylation of this histidine is a prerequisite for ADP-mediated inactivation through phosphorylation of a threonine residue from the beta-phosphate of ADP. It is demonstrated that diethylpyrocarbonate (which forms a derivative with histidine residues) prevents [32P]phosphoenolpyruvate-dependent labeling (catalytic labeling) and [beta-32P]ADP-dependent labeling (inactivation labeling) of the enzyme. In addition, it is demonstrated that oxalate, an analog of pyruvate, competitively inhibits ADP-dependent inactivation with respect to ADP. The significance of these results is discussed with regard to the mechanism of regulation of pyruvate,Pi dikinase in vivo.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites; D002384:Catalysis; D055598:Chemical Phenomena; D002621:Chemistry; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D006639:Histidine / Q000302:isolation & purification* / Q000378:metabolism; D010070:Oxalates / Q000494:pharmacology; D019815:Oxalic Acid; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D010777:Photochemistry; D011772:Pyruvate, Orthophosphate Dikinase / Q000378:metabolism*; D003313:Zea mays / Q000201:enzymology
chemical_list: D000596:Amino Acids; D010070:Oxalates; D006639:Histidine; D000244:Adenosine Diphosphate; D019815:Oxalic Acid; D010770:Phosphotransferases; D011772:Pyruvate, Orthophosphate Dikinase; D004047:Diethyl Pyrocarbonate