Phosphorylation of type-L pyruvate kinase in intact hepatocytes. Localisation of the phosphorylation site in response to both glucagon and the Ca2+-linked agonist phenylephrine.

Pyruvate kinase is one of the enzymes which can be phosphorylated by stimulation of the cell with either glucagon or Ca2+-linked hormones. Whether these two classes of hormones phosphorylate the same site on the enzyme is unclear. Our results demonstrate that isolation of [32P]phosphorylated type-L pyruvate kinase from glucagon-treated hepatocytes followed by aspartyl-prolyl cleavage yields a [32P]phosphorylated peptide of Mr 17,000. This fragment is also phosphorylated in response to the Ca2+-mediated agonist phenylephrine.