The in vitro modification of phosphorylated pyruvate kinase by a Ca2+-activated protease from rat liver.
A Ca/+-activated protease from rat liver cell sap was prepared. It was shown to act on rat liver pyruvate kinase that had been phosphorylated by the catalytic subunit of cyclic AMP-dependent protein kinase, the activity being optimum at neutral pH. The modified pyruvate kinase had the same Vmax as the phosphoenzyme but showed a lower affinity for the substrate phosphoenolpyruvate. The possibility that this proteolytic attack is the step that initiates further degradation in the cell is discussed.
D000818:Animals; D002118:Calcium / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D010447:Peptide Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D011770:Pyruvate Kinase / Q000378:metabolism*; D051381:Rats
D011770:Pyruvate Kinase; D010447:Peptide Hydrolases; D002118:Calcium