2 research outputs found
Structure-Guided, Single-Point Modifications in the Phosphinic Dipeptide Structure Yield Highly Potent and Selective Inhibitors of Neutral Aminopeptidases
Seven crystal structures of alanyl
aminopeptidase from <i>Neisseria meningitides</i> (the etiological
agent of meningitis, <i>Nm</i>APN) complexed with organophosphorus
compounds were resolved
to determine the optimal inhibitorâenzyme interactions. The
enantiomeric phosphonic acid analogs of Leu and hPhe, which correspond
to the P1 amino acid residues of well-processed substrates, were used
to assess the impact of the absolute configuration and the stereospecific
hydrogen bond network formed between the aminophosphonate polar head
and the active site residues on the binding affinity. For the hPhe
analog, an imperfect stereochemical complementarity could be overcome
by incorporating an appropriate P1 side chain. The constitution of
P1â˛-extended structures was rationally designed and the lead,
phosphinic dipeptide hPhePĎÂ[CH<sub>2</sub>]ÂPhe, was modified
in a single position. Introducing a heteroatom/heteroatom-based fragment
to either the P1 or P1Ⲡresidue required new synthetic pathways.
The compounds in the refined structure were low nanomolar and subnanomolar
inhibitors of <i>N. meningitides</i>, porcine and human
APNs, and the reference leucine aminopeptidase (LAP). The unnatural
phosphinic dipeptide analogs exhibited a high affinity for monozinc
APNs associated with a reasonable selectivity versus dizinc LAP. Another
set of crystal structures containing the <i>Nm</i>APN dipeptide
ligand were used to verify and to confirm the predicted binding modes;
furthermore, novel contacts, which were promising for inhibitor development,
were identified, including a ĎâĎ stacking interaction
between a pyridine ring and Tyr372
<i>Bacillus anthracis</i> Inosine 5â˛-Monophosphate Dehydrogenase in Action: The First Bacterial Series of Structures of Phosphate Ionâ, Substrateâ, and Product-Bound Complexes
Inosine 5â˛-monophosphate dehydrogenase (IMPDH)
catalyzes
the first unique step of the GMP branch of the purine nucleotide biosynthetic
pathway. This enzyme is found in organisms of all three kingdoms.
IMPDH inhibitors have broad clinical applications in cancer treatment,
as antiviral drugs and as immunosuppressants, and have also displayed
antibiotic activity. We have determined three crystal structures of <i>Bacillus anthracis</i> IMPDH, in a phosphate ion-bound (termed
âapoâ) form and in complex with its substrate, inosine
5â˛-monophosphate (IMP), and product, xanthosine 5â˛-monophosphate
(XMP). This is the first example of a bacterial IMPDH in more than
one state from the same organism. Furthermore, for the first time
for a prokaryotic enzyme, the entire active site flap, containing
the conserved Arg-Tyr dyad, is clearly visible in the structure of
the apoenzyme. Kinetic parameters for the enzymatic reaction were
also determined, and the inhibitory effect of XMP and mycophenolic
acid (MPA) has been studied. In addition, the inhibitory potential
of two known <i>Cryptosporidium parvum</i> IMPDH inhibitors
was examined for the <i>B. anthracis</i> enzyme and compared
with those of three bacterial IMPDHs from <i>Campylobacter jejuni</i>, <i>Clostridium perfringens</i>, and <i>Vibrio cholerae</i>. The structures contribute to the characterization of the active
site and design of inhibitors that specifically target <i>B.
anthracis</i> and other microbial IMPDH enzymes