Interaction of formycin A-5'-triphosphate with pyruvate carboxylase.
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.
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001667:Binding, Competitive; D002645:Chickens; D005573:Formycins / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D011766:Pyruvate Carboxylase / Q000378:metabolism*; D012265:Ribonucleotides / Q000494:pharmacology*; D012756:Sheep; D013050:Spectrometry, Fluorescence
D000903:Antibiotics, Antineoplastic; D005573:Formycins; D012265:Ribonucleotides; C021683:formycin 5'-phosphate; D011766:Pyruvate Carboxylase