A  1010 Rate Enhancement of Phosphodiester Hydrolysis by a Di-Zinc Aminopeptidase
—Transition-State Analogues as Substrates?**
Angew. Chem. Intl. Engl. Ed. 1999, 38, 2914-2916.

Hyun Ik Park and Li-June Ming*

Department of Chemistry and Institute for Biomolecular Science
University of South Florida
Tampa, Florida 33620-5250

Although tetrahedral phospho-moieties often serve as transition-state analogues in peptide hydrolysis, we found that bis-p-nitrophenylphosphate (BNPP) can be effectively hydrolyzed into nitrophenylphosphate and p-nitrophenol by a di-Zn aminopeptidase from Streptomyces griseus (sAP).  This di-Zn enzyme gives a remarkable specific activity 33.7 nmol min–1 mg–1 toward the hydrolysis of 1 mM BNPP comparable to some native phosphodiesterases, and a second rate constant kcat/Km = 100 M–1s–1 that is >106 times superior to several Zn2+-containing chemical models. The rate enhancement of BNPP hydrolysis by sAP is about 1010 when compared with the first order rate constant of BNPP auto-hydrolysis.  This study indicates that sAP can serve as a novel dinuclear model to provide further insight into dinuclear hydrolysis in chemical and biological systems.

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