The interaction of non-phosphorylated L-type pyruvate kinase (L-PK) with fructose 1,6-bisphosphate (FBP),
which is an allosteric activator of the phosphorylated enzyme, and peptides that mimic the phosphorylatable N-terminal
regulatory domain of the enzyme, was studied. It was found that the catalytic activity of the enzyme was not enhanced in
the presence of FBP, and this ligand acted as a relatively weak reversible inhibitor of the enzyme activity in the micromolar
concentration range. The phosphorylation site analogue peptides RRASVA and RRAAVA had no effect on the activity
of the enzyme, while the phosphorylated peptide RRAS(Pi)VA reversibly inhibited the enzyme and this process was characterised
by the Ki value 47 μM. As the phosphorylated form of L-PK is a subject of significant allosteric regulation by
FBP, it was concluded that phosphorylation should function as a molecular switch of the allosteric properties of this enzyme.
Keywords: Allosteric effector, fructose 1, 6-bisphosphate, L-type pyruvate kinase, N-terminal domain, peptide, phosphoenolpyruvate.
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