Effects of phosphorylation on the kinetic properties of rat liver ATP-citrate lyase.
Homogeneous rat liver ATP-citrate lyase (EC 4.1.3.8) was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase. In agreement with other workers, the maximum level of phosphorylation that we observed was approx. 2 mol/mol of tetramer. Phosphorylated and non-phosphorylated forms of ATP-citrate lyase were prepared. Their kinetic properties were examined using an assay system in which the concentrations of Mg.ATP, magnesium.citrate and CoA were varied systematically at a constant concentration of Mg2+. The phosphorylated form had a two-fold higher Km for Mg.ATP than did the non-phosphorylated form, but no other kinetic differences between the two forms were detected. When ATP-citrate lyase was assayed at a concentration of Mg.ATP well below Km, it was found that phosphorylation of the enzyme correlated well with a decrease of approx. 50% in its activity. This is the first demonstration that phosphorylation can affect the activity of ATP-citrate lyase.
D001275:ATP Citrate (pro-S)-Lyase / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D013997:Time Factors
D000255:Adenosine Triphosphate; D001275:ATP Citrate (pro-S)-Lyase; D011494:Protein Kinases