ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P118. Dizinc(II) Pyrazolate Complexes as Functional Models of Enzyme
Active Sites
A. Maciąg a , L. V. Penkova b , F. Meyer c , I. O. Fritsky b and H. Kozłowski a
a
University of Wroclaw, Faculty of Chemistry, 14 F. Joliot-Curie, 50-383 Wroclaw, Poland
e-mail: annam@wcheto.chem.uni.wroc.pl
b
National Taras Shevchenko University, Department of Inorganic Chemistry, Volodymyrska str. 64, Kyiv 01033,
Ukraine;
c
Georg-August-Universität Göttingen, Institut für Anorganische Chemie, Tammannstr. 4, 37077 Göttingen,
Germany;
Various hydrolytic enzymes that mediate the cleavage of biologically important phosphate esther bond are
known to contain two proximal zinc ions within their active sites. Examples include some metallo-β lactamases,
several aminopeptidases, phosphotriesterase, and alkaline phosphatase. Despite intensive investigation, still not
much is known about the mechanism of enzyme action. Metal complexes with small organic molecules that
resemble the active sites of the enzymes may provide some insight into the basic principles that govern the
enzymatic activity.
Two factors are crucial in hydrolytic activity of dizinc complexes. One is the zinc – zinc separation distance, and
the other is the ability to generate strongly nucleophilic hydroxide group by lowering the pKa of bound water.
Pyrazolate-based ligands with chelating side arms in the 3- and 5-positions of the heterocyclic ring have a high
tendency to span two metal ions, and the metal-metal separations can be adjusted by modification of chelating
substituents [1].
In this work, the RNA model substrate, 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) was exploited to
study the hydrolytic behavior of dizinc pyrazolate complexes. The increase in product concentration (pnitrophenolate
anion) was followed by UV-Vis spectroscopy. The obtained results were correlated by
potentiometric and spectroscopic methods to reveal the active compounds.
References:
[1] B. Bauer-Siebenlist, F. Meyer, E. Farkas, D. Vidovic, S. Dechert, Chem. Eur. J., 11, 4349 (2005)
_____________________________________________________________________
237