2School of Chemistry, Lomonosov Moscow State University, Moscow, 119899 Russia
* To whom correspondence should be addressed.
Received June 9, 1998; Revision received June 26, 1998
Magnesium-supported PPi hydrolysis by the mutant Asp-67Asn E. coli pyrophosphatase at saturating PPi and metal-activator concentrations in the presence of NaF is followed by a gradual decrease in the initial rate of PPi hydrolysis. The reaction occurs in two steps: first a complex containing enzyme, pyrophosphate, magnesium, and fluoride ions is immediately formed, then its conformation changes slowly. This enzyme--substrate complex stabilized by fluoride is partially active and can be isolated by the removal of excess fluoride by gel-filtration.
KEY WORDS: inorganic pyrophosphatase, Escherichia coli, inhibition by fluoride, enzyme--substrate complex