Formation of a beta-aspartyl phosphate intermediate by the vanadate-sensitive ATPase of Streptococcus faecalis

The vanadate-sensitive membrane ATPase of Streptococcus faecalis forms, as part of the reaction cycle, an acylphosphate intermediate. The phosphorylated amino acid residue was identified by reducing the purified reconstituted phosphoenzyme with [3H]borohydride, followed by acid hydrolysis of the protein and quantitative amino acid analysis. Tritiated homoserine was found to be the resulting reaction product, generated through the reduction of a beta-aspartyl phosphate residue. The S. faecalis ATPase thus forms the same phosphorylated intermediate as a number of eukaryotic transport ATPases and appears to be related to these enzymes.