Angewandte
Chemie
hydrolysis of the initially formed phosphorylcholine. AlkP is a
zinc phosphoesterase that has been traditionally related to
PC-PLCBc because it also includes a trinuclear active site,
although structural differences are evident. It is noteworthy
that this enzyme was not inhibited by compounds 3–10 (data
not shown) even at concentrations two orders of magnitude
higher (0.5 mm) than those required for 50% inhibition of
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active site is not the only element required for inhibition by a-
aminohydroxamates. These results could be related to the
different catalytic mechanism operating in AlkP, which
187.
[
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[
23]
involves a serine phosphate intermediate
that is subse-
quently hydrolyzed to the final phosphate product. In
contrast, the accepted mechanism for PC-PLCBc and related
aminopeptidases involves a direct attack of water or a
hydroxide ion on the phosphorus atom of phosphatidylcho-
line or on the carbonyl amide group. To stress the structural
[
[
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differences of AlkP and PC-PLC , the absence of a
Bc
carboxylate group bridging the zinc ions in the AlkP active
site and the presence of a magnesium ion in the place of the
third zinc center is noteworthy.
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[
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In summary, a new family of PC-PLCBc inhibitors has been
disclosed by finding similarities among fold- and sequence-
unrelated proteins, which, however, possess structurally and
chemically related active sites. It is interesting to note the
evolutionary convergence of the active-site architecture in
dinuclear zinc aminopeptidases and lipid phosphohydrolases
that leads to a similar solution for catalyzing the hydrolysis of
amides and phosphodiesters. Appropriate modifications of
the inhibitors to selectively address either phospholipase or
aminopeptidase enzymes are to be found in future work. The
results obtained show that when the structural determinants
of the desired biological activity are available, alternative lead
discovery procedures can be envisaged. With all necessary
caution, we consider that the approach presented here may be
useful not only for the identification of new inhibitors for a
particular enzyme but also to unravel structurally related
targets for known enzyme inhibitors.
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Org. Chem. 2000, 65, 4509 – 4514.
Received: June 26, 2003
Revised: October 21, 2003 [Z52241]
[
Keywords: hydrolases · inhibitors · metalloenzymes ·
.
protein structures · zinc
[
[
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4
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8
1
[
2] Although PC-PLCBc is not toxic for mammals, it is structurally
and functionally related to enzymatic pathogenic bacterial toxins
such as the Clostridium perfringens gas gangrene a toxin: C. E.
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4
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