title: Pig liver pyruvate carboxylase. The reaction pathway for the decarboxylation of oxaloacetate.
abstract: 1. The reaction pathway for the decarboxylation of oxaloacetate, catalysed by pig liver pyruvate carboxylase, was studied in the presence of saturating concentrations of K(+) and acetyl-CoA. 2. Free Mg(2+) binds to the enzyme in an equilibrium fashion and remains bound during all further catalytic cycles. MgADP(-) and P(i) bind randomly, at equilibrium, followed by the binding of oxaloacetate. Pyruvate is released before the ordered steay-state release of HCO(3) (-) and MgATP(2-). 3. These results are entirely consistent with studies on the carboxylation of pyruvate presented in the preceding paper (Warren & Tipton, 1974b) and together they allow a quantitative description of the reaction mechanism of pig liver pyruvate carboxylase. 4. In the absence of other substrates of the back reaction pig liver pyruvate carboxylase will decarboxylate oxaloacetate in a manner that is not inhibited by avidin. 5. Reciprocal plots involving oxaloacetate are non-linear curves, which suggest a negatively co-operative interaction between this substrate and the enzyme.
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D001360:Avidin / Q000378:metabolism; D001639:Bicarbonates / Q000096:biosynthesis; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000378:metabolism; D008954:Models, Biological; D010071:Oxaloacetates / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011485:Protein Binding; D011766:Pyruvate Carboxylase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011773:Pyruvates / Q000096:biosynthesis; D013552:Swine
chemical_list: D001639:Bicarbonates; D010071:Oxaloacetates; D010710:Phosphates; D011773:Pyruvates; D001360:Avidin; D000244:Adenosine Diphosphate; D000105:Acetyl Coenzyme A; D000255:Adenosine Triphosphate; D011766:Pyruvate Carboxylase; D008274:Magnesium; D011188:Potassium