Phosphorylation of recombinant human ATP:citrate lyase by cAMP-dependent protein kinase abolishes homotropic allosteric regulation of the enzyme by citrate and increases the enzyme activity. Allosteric activation of ATP:citrate lyase by phosphorylated sugars.

摘要: Recombinantly expressed human ATP:citrate lyase was purified from E. coli, and its kinetic behavior characterized before after phosphorylation. Cyclic AMP-dependent protein kinase catalyzed the incorporation of only 1 mol phosphate per mole enzyme homotetramer, glycogen synthase kinase-3 incorporated an additional 2 into phosphorylated protein. Isoelectric focusing revealed that all phosphates were one four subunits. Phosphorylation resulted in a 6-fold increase V(max) conversion citrate dependence sigmoidal, displaying negative cooperativity, to hyperbolic. The recombinant is more similar isolated mammalian tissues than unphosphorylated with respect K(m) for citrate, CoA, ATP, specific activity. Fructose 6-phosphate found be potent activator (60-fold) enzyme, half-maximal activation at 0.16 mM, which results decrease apparent as well reaction. Thus, activity regulated vitro allosterically by sugars covalently