The kinetic mechanism of yeast phosphoenolpyruvate carboxykinase.
The kinetic mechanism of yeast phosphoenolpyruvate carboxykinase, in the physiological direction, has been determined. Product inhibition using KHCO3 showed competitive inhibition, when both oxalacetate (OAA) and ATP were varied. Phosphoenolpyruvate showed noncompetitive inhibition against OAA, and competitive inhibition with respect to ATP. Conversely, ADP showed competitive inhibition against OAA and noncompetitive inhibition vs. ATP. Dead-end inhibition studies with beta-sulfopyruvate showed competitive inhibition against OAA and noncompetitive inhibition vs. ATP. Ethene-ATP exhibited competitive inhibition against ATP and noncompetitive inhibition with respect to OAA. These results are consistent with a random Bi-Ter mechanism with the formation of two abortive complexes: enzyme-ATP-ADP and enzyme-OAA-PEP.
Jabalquinto
A M
AM
Departamento de Química, Facultad de Ciencia, Universidad de Santiago de Chile.
Cardemil
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E
D000244:Adenosine Diphosphate / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D001667:Binding, Competitive; D007700:Kinetics; D010071:Oxaloacetates / Q000737:chemistry; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000037:antagonists & inhibitors / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
D010071:Oxaloacetates; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D010729:Phosphoenolpyruvate Carboxykinase (GTP)