The kinetic mechanism of yeast phosphoenolpyruvate carboxykinase |
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| Institution: | 1. Department of Life Sciences, National Chung-Hsing University, Taichung, Taiwan;2. Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan;3. Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan;4. Department of Dermatology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan;5. Institute of Microbiology and Immunology and Division of Allergy, Immunology and Rheumatology, Chung Shan Medical University and Hospital, Taichung, Taiwan;6. Institute of Genomics and Bioinformatics, National Chung-Hsing University, Taichung, Taiwan |
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| Abstract: | 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 β-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. |
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