Hexameric,Trimeric, Dimeric,and Monomeric Forms of Inorganic Pyrophosphatase from Escherichia coli

The conditions were found for obtaining trimeric, dimeric, and monomeric forms of the Escherichia coli inorganic pyrophosphatase from its native hexameric form. Interconversions of the oligomers were studied, and rate constants for their dissociation and association were determined. All forms were found to be catalytically active, with the activity decreasing in the following order: hexamer–trimer–dimer–monomer. The activity of trimeric and dimeric forms was high enough to study and to compare their catalytic properties. The monomeric form of the enzyme was unstable.