Interaction of formycin A-5'-triphosphate with pyruvate carboxylase |
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Authors: | P V Attwood J H Coates J C Wallace |
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Institution: | 1. Department of Biochemistry, University of Adelaide, GPO Box 498, Adelaide, 5001, Australia;2. Department of Physical and Inorganic Chemistry, University of Adelaide, GPO Box 498, Adelaide, 5001, Australia |
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Abstract: | Formycin triphosphate (FTP), a fluorescent analogue of ATP, is a competitive inhibitor of chicken liver pyruvate carboxylase with respect to ATP. The chicken liver enzyme is unable to utilise FTP as a substrate at a measureable rate, but FTP is a poor substrate for the sheep liver enzyme. When FTP binds to the enzyme, its fluorescence is enhanced and in this way the formation of enzyme-FTP complexes can be monitored. Using this property of FTP, the effect of Mg2+ and acetyl-CoA on the binding of nucleoside triphosphates to the chicken liver enzyme was examined. Mg2+ was found to enhance the binding of FTP whilst acetyl-CoA reduced the fluorescence intensity of a mixture of Mg2+, enzyme and FTP. Most probably, this was caused by a conformational change in the enzyme which changed the environment of the fluorophore. |
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Keywords: | Pyruvate carboxylase Formycin triphospate |
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