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Figure 3.
Fig. 3. Comparison of amidase active sites. (a) A-subunit of
A. aeolicus GatCAB showing the acyl-enzyme intermediate of
substrate Gln with Ser171. (b) Active site of MAE2 in complex
with product malonate.^23 Arg158 in the amidase core region
interacts with a carboxyl group of malonate (Mal). (c) Active
site of FAAH with the inactivator methoxy arachidonyl
phosphonate (MAP).^26 The phosphonate of the covalent adduct at
nucleophilic Ser241 mimics the tetrahedral intermediate of the
hydrolytic reaction. Aromatic and aliphatic residues in the
substrate binding pocket are indicated. (d) Active site of PAM
in complex with the inhibitor chymostatin (CST).^25 For each
enzyme, the amidase core region (residues 62–192 of GatA,
residues 52–176 of MAE2, residues 132–262 of FAAH, and
residues 113–246 of PAM) is colored blue, and residues outside
the core region are colored green. Residues in the
Ser–cisSer–Lys catalytic scissors of each enzyme and those
interacting with ligands are shown as thin sticks; adducts and
ligands are shown in ball-and-stick form with atomic coloring:
gray, C; red, O; blue, N; orange, P. Hydrogen bonds are shown as
dashed lines.
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