Purification and characterization of an ATP-dependent protein kinase fromStreptococcus faecalis

An enzyme catalyzing the ATP-dependent phosphorylation of HPr of the bacterial phosphotransferase system has been purified from Streptococcus faecalis. Size exclusion chromatography and sodium dodecyl sulfate (SDS) polyacrylamide gels revealed an Mr of 65000. Beside HPr of S. faecalis the protein kinase also phosphorylates HPr of Streptococcus lactis, Streptococcus pyogenes, Bacillus subtilis and Streptococcus aureus, but not HPr of Escherichia coli. The kinase is largely inhibited by Pi and EDTA. Mg2+ and Mn2+ could overcome inhibition by EDTA. 2-Phosphoglycerate and glucose-6-phosphate, previously reported to stimulate kinase activity in crude extracts, had no effect on the purified enzyme. Fructose-1,6-diphosphate stimulated the protein kinase.