title: Regulation at the phosphoenolpyruvate branchpoint in Azotobacter vinelandii: phosphoenolpyruvate carboxylase.
abstract: Phosphoenolpyruvate carboxylase (EC 4.1.1.31) from Azotobacter vinelandii, like the corresponding enzyme from other organisms, is activated by acetyl coenzyme A and inhibited by l-aspartate. Both modifiers affect primarily the affinity of the enzyme for phosphoenolpyruvate. This is the first enzyme with a strictly anaplerotic (intermediate-replacing) function to be tested for response to the adenylate energy charge; it is entirely insensitive to variation in charge. The results suggest that carboxylation of phosphoenolpyruvate in this organism is controlled by negative feedback from aspartate and by the stimulatory effect of acetyl coenzyme A. The adenylate energy charge may be expected to affect the rate of this reaction indirectly through its effects on the concentrations of acetyl coenzyme A and l-aspartate.
mesh_terms: D001224:Aspartic Acid / Q000494:pharmacology; D001395:Azotobacter / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D002482:Cellulose; D011232:Chemical Precipitation; D003065:Coenzyme A / Q000494:pharmacology; D003470:Culture Media; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D010756:Phosphoric Acids / Q000378:metabolism*; D011770:Pyruvate Kinase / Q000302:isolation & purification / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds; D013237:Stereoisomerism; D013431:Sulfates
chemical_list: D003470:Culture Media; D010756:Phosphoric Acids; D011773:Pyruvates; D000644:Quaternary Ammonium Compounds; D013431:Sulfates; D001224:Aspartic Acid; D002482:Cellulose; D011770:Pyruvate Kinase; D002262:Carboxy-Lyases; D008274:Magnesium; D003065:Coenzyme A