H. Yang, J. C. Sherman / Bioorg. Med. Chem. Lett. 23 (2013) 1752–1753
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Table 1
Esterase activity on p-nitrophenyl butyrate (phosphate buffer, pH 7)a
System
Rate/DmAbsU410nm min
Cavitein 0.1 mM
Peptide 0.4 mM
Uncatalyzed
37
7.9
2.1
a
The reaction was conducted in phosphate buffer, pH 7, room temperature.
enhanced by of the free peptide over background is about fourfold
while that of the cavitein over background is close to 18-fold.
We have determined that a histidine-containing cavitein has a
significant effect in catalyzing ester hydrolysis of p-nitrophenyl
butyrate. More work is envisioned: (1) investigation of the mecha-
nism of this reaction: we can explore ester hydrophobicity to see if
the hydrophobic centre in the cavitein influences the esterase
activity; (2) optimization: alter the sequence to obtain a better
esterase activity; (3) other activity: we can also explore this histi-
dine-containing cavitein in amide hydrolysis reactions.
Figure 1. An arylthiol cavitand.
Experimental: The initial rate was obtained from a UV spectro-
photometric assay for the p-nitrophenolate formed during hydro-
lysis using the absorbance signal at 410 nm at room temperature.
The initial rates were determined through linear regression on data
taken after 10 min, where the kinetic plots were linear.
The stock solution of p-nitrophenyl butyrate (100 mM) was pre-
pared and wrapped in aluminium foil at 4 °C. The solution was di-
luted with phosphate buffer (0.5 M, pH 7) 100 times before use.
Both the free peptide (0.4 mM) and cavitein (0.1 mM) were dis-
solved in this diluted solution.
Figure 2. Chloroacetylated peptide linked arylthiol cavitand.
Acknowledgments
We would like to thank the Natural Sciences and Engineering
Research Council of Canada (N.S.E.R.C.) for financial support, the
bioservice of University of British Columbia for the data collected
on Varian Cary4000 UV/vis absorption spectrophotometer.
References and notes
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The data in Table 1 shows that both the peptide and cavitein are
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