Presteady State Kinetics of Phosphoro - thioate Hydrolysis by Alkaline Phosphatase RATE - LIMITING DEPHOSPHORYLATION
نویسنده
چکیده
The hydrolysis of 0-p-phenylazophenylphosphorothioate by Escherichia coli alkaline phosphatase was studied by the stopped-flow technique. “Burst” kinetics is observed at both acid and basic pH, suggesting that a step following thiophosphorylation is rate-limiting at all pH values. At pH 8.5, activation of a second active site on the enzyme dimer is observed in the transient phase as subsrrate concentration is increased. The rate of the transient phase, however, decreases at high substrate concentration, suggesting that negative cooperativity exists between the two active sites. The implications of these results for the mechanism of hydrolysis of both 0-phosphorothioate and phosphate monoesters by alkaline phosphatase are discussed.
منابع مشابه
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