Inhibition of the <i>dapE</i>-Encoded <i>N</i>‑Succinyl‑l,l‑diaminopimelic
Acid Desuccinylase from <i>Neisseria meningitidis</i> by l‑Captopril
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Abstract
Binding of the competitive inhibitor l-captopril to the <i>dapE</i>-encoded <i>N</i>-succinyl-l,l-diaminopimelic acid desuccinylase
from <i>Neisseria meningitidis</i> (<i>Nm</i>DapE)
was examined by kinetic, spectroscopic,
and crystallographic methods. l-Captopril, an angiotensin-converting
enzyme (ACE) inhibitor, was previously shown to be a potent inhibitor
of the DapE from <i>Haemophilus influenzae</i> (<i>Hi</i>DapE) with an IC<sub>50</sub> of 3.3 μM and a measured <i>K</i><sub>i</sub> of 1.8 μM and displayed a dose-responsive
antibiotic activity toward <i>Escherichia coli</i>. l-Captopril is also a competitive inhibitor of <i>Nm</i>DapE with a <i>K</i><sub>i</sub> of 2.8 μM. To examine
the nature of the interaction of l-captopril with the dinuclear
active site of DapE, we have obtained electron paramagnetic resonance
(EPR) and magnetic circular dichroism (MCD) data for the enzymatically
hyperactive Co(II)-substituted forms of both <i>Hi</i>DapE
and <i>Nm</i>DapE. EPR and MCD data indicate that the two
Co(II) ions in DapE are antiferromagnetically coupled, yielding an <i>S</i> = 0 ground state, and suggest a thiolate bridge between
the two metal ions. Verification of a thiolate-bridged dinuclear complex
was obtained by determining the three-dimensional X-ray crystal structure
of <i>Nm</i>DapE in complex with l-captopril at
1.8 Å resolution. Combination of these data provides new insights
into binding of l-captopril to the active site of DapE enzymes
as well as important inhibitor–active site residue interaction’s.
Such information is critical for the design of new, potent inhibitors
of DapE enzymes