Gene links:
No gene identifiers were provided.
Description:
Enolase (ENO) is a glycolytic enzyme located in the cytosol, also in
trypanosomatids.
Validation Glycolysis is essential for bloodstream-form trypanosomes
[reviewed in 1]. By a large number of experiments, involving enzyme inhibitors
and RNAi, it has been shown that approximately 50% reduction of the glycolytic
flux is sufficient to kill the parasites [2,3]. The contribution of ENO to the
control of the glycolytic flux in bloodstream-form T. brucei has been
determined by RNAi; partial depletion of the enzyme activity was shown to be
sufficient to kill the parasites [2].
Description
Enzyme Properties. The enzyme is in T. brucei encoded by a single gene. It
has been expressed in Escherichia coli; the protein has been purified and
kinetically characterized [4]. Despite the considerable degree of conservation
(58% amino-acid sequence identity between the T. brucei ENO and its three human
homologues), structure modelling showed three interesting residues near the
catalytic site of the Trypanosoma enzyme (conserved in all trypanosomatids
analyzed) but absent from the human enzymes [4]. The chemical characteristics
of the side-chains of these residues (two Cys and one Lys) offer the potential
for selective drug targeting. Indeed, at least one of the Cys residues was
shown to be solvent accessible [5].
Crystal Structure. Crystal structures of the apo-enzyme and the enzyme
complexed with its substrate PEP, sulphate and the high-affinity inhibitors
phosphonoacetohydroxamate (PAH) and fluoro-PAH have been determined [5,6; PDB
accession codes 10EP, 2PTY, 2PTX, 2PTW, 2PTZ, 2PU0 and 2PT1]. These
structures, in conjunction with molecular dynamics, revealed a structural
flexibility of the active site and confirmed the accessibility of the unique
Lys residue too.
Drug Discovery. PAH is a known transition-state analogue of enolases that
inhibits by binding with very high affinity in the active site (Ki for T.
brucei enolase = 15 nM). Crystal structure analysis suggests the possibility
of providing selectivity towards the parasite enzyme by enlarging this
non-selective inhibitor to reach the potentially modifiable side chains of
residues not far from the catalytic site, notably Lys155, through a tunnel from
the small enclosed catalytic site [6].
- Verlinde et al, Drug Resistance Updates (2001) 4, 50-65.
- Albert et al, J. Biol. Chem. (2005) 280, 28306-28315.
- Haanstra et al, Proc. 11th Int. Congr. Parasitol. Glasgow (ISBN 88-7587-273-2), (2006) pp. 91-96.
- Hannaert et al, Eur. J. Biochem. (2003) 270, 3205-3213.
- da Silva Giotto et al, J. Mol. Biol. (2003) 331, 653-665.
- de A. S. Navarro et al, FEBS J. (2007) 274, 5077-5089.
Target ID: geneDB number = Tb10.70.4740 EC number (if enzyme) = EC 4.2.1.11 target name = ENO
Validation: Genetic OR chemical evidence
Assay status: Assay exists but not yet in microtitre plate format
Availability: Can be expressed > 1 mg/L in soluble, active form
Activity: Significant (>= 1 full time person)
No references provided.