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

Eurobic9, 2-6 September, 2008, Wrocław, Poland
SL22. A Biomimetic System for Serine Protease Enzymes
A. AlAgha a , O.R. Nunez a,b , F. Butler a , K.B Nolan a
a Centre for Synthesis and Chemical Biology, Department of Pharmaceutical & Medicinal Chemistry, Royal
College of Surgeons in Ireland, St. Stephen’s Green, Dublin 2, Ireland
e-mail: kbnolan@rcsi.ie
b Departmento de Procesos y Sistemas, Universidad Simon Bolivar, Caracas, Venezuela.
In general, peptides undergo very slow hydrolysis, as demonstrated by the fact that the half-time for
glycylglycine hydrolysis at neutral pH, 25 o C is ~350 years [1]. Similarly glycylserine at pH = ~ 7 (HEPES
buffer, D2O) undergoes no appreciable hydrolysis after ~40 h. However in the presence of serine protease
enzymes the hydrolysis of this and related substrates is catalysed by peptide group activation and by
participation of the nucleophilic serine -OH group and water in hydrolysis. The nucleophilicity of this group is
further enhanced by hydrogen bonding with the terminal carboxylate. We report here a biomimetic system for
catalysis by this enzyme.
In the presence of zinc(II), glycylserine under the same reaction conditions as above undergoes hydrolysis with a
half-time of ~26h, which is much more rapid than the free peptide. In this system the glycyl residue is bidentate,
complexing through the amino and peptide O groups. The complex formed produces a 1 H NMR signal upfield
by ~0.2 ppm for the glycyl –CH2 group relative to the uncomplexed peptide. Even though the 1 H NMR signals of
the HEPES buffer overlap with some of the peptide signals, the glycylserine –CH group (~4.21 ppm) as well as
the signals of the serine –CH group (~3.6 ppm) and the glycine –CH2 group (~3.2 ppm) in the hydrolysis product
do not overlap with buffer signals. This allowed a study of the reaction kinetics by 1 H NMR spectroscopy.
The catalysis observed in the Zn(II)-glycylserine hydrolysis is due to a combination of electrophilic catalysis by
the metal ion and an internal general base catalysis of water promoted by the Ser –COO--- H---O - (see Figure).
This is under further investigation.
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74
Zn
H 2 N
O
H
O
NH
Acknowledgement: We thank the Irish Government under its Programme for Research in Third Level
Institutions for support.
Reference:
[1] A. Radizicka, R. Wolfenden, J.Am.Chem.Soc. 1996, 118, 6105.
H
O
O
H
O -