Hexameric inorganic pyrophosphatase of Escherichia coli contains about 1 80187-N/asset/equation/feb2001457939080187n-math-si1.gif?v=1&s=dbdf5f4d2a62a05d5924e0990bc29d4dc7432696)
of ‘structural’ pyrophosphate, which survives gel nitration and prolonged incubation with Mg2+, does not exchange with medium phosphate and pyrophosphate but is removed with 0.8 M perchloric acid. The site of pyrophosphate binding seems to be another than the active site. An additional 0.9 mol of enzyme-bound pyrophosphate is formed in the presence of phosphate and Mg2+ but this pyrophosphate is in fast equilibrium with medium phosphate and appears to be bound to the active site.
