Constitutive inorganic pyrophosphatase as a reciprocal regulator of three inducible enzymes in Escherichia coli.

Background: Previous studies have demonstrated the formation of stable complexes between inorganic pyrophosphatase (PPase) and three other Escherichia coli enzymes - cupin-type phosphoglucose isomerase (cPGI), class I fructose-1,6-bisphosphate aldolase (FbaB) and l-glutamate decarboxylase (GadA).

Methods: Here, we determined by activity measurements how complex formation between these enzymes affects their activities and oligomeric structure.

Results: cPGI activity was modulated by all partner proteins, but none was reciprocally affected by cPGI.

A novel, cupin-type phosphoglucose isomerase in Escherichia coli.

Background: Escherichia coli cells contain a homolog of presumed 5-keto-4-deoxyuronate isomerase (KduI) from pectin-degrading soil bacteria, but the catalytic activity of the E. coli protein (o-KduI) was never demonstrated.

Methods: The known three-dimensional structure of E.