Background
Amoebiasis, caused by
Entamoeba histolytica
infection, is a global public health problem. However, available drugs to treat amoebiasis are currently limited, and no effective vaccine exists. Therefore, development of new preventive measures against amoebiasis is urgently needed.
Methodology/Principal findings
Here, to develop new drugs against amoebiasis, we focused on
E
.
histolytica
adenosine 5′-phosphosulfate kinase (EhAPSK), an essential enzyme in
Entamoeba
sulfolipid metabolism. Fatty alcohol disulfates and cholesteryl sulfate, sulfolipids synthesized in
Entamoeba
, play important roles in trophozoite proliferation and cyst formation. These processes are closely associated with clinical manifestation and severe pathogenesis of amoebiasis and with disease transmission, respectively. We validated a combination approach of
in silico
molecular docking analysis and an
in vitro
enzyme activity assay for large scale screening. Docking simulation ranked the binding free energy between a homology modeling structure of EhAPSK and 400 compounds. The 400 compounds were also screened by a 96-well plate-based
in vitro
APSK activity assay. Among fifteen compounds identified as EhAPSK inhibitors by the
in vitro
system, six were ranked by the
in silico
analysis as having high affinity toward EhAPSK. Furthermore, 2-(3-fluorophenoxy)-N-[4-(2-pyridyl)thiazol-2-yl]-acetamide, 3-phenyl-N-[4-(2-pyridyl)thiazol-2-yl]-imidazole-4-carboxamide, and auranofin, which were identified as EhAPSK inhibitors by both
in silico
and
in vitro
analyses, halted not only
Entamoeba
trophozoite proliferation but also cyst formation. These three compounds also dose-dependently impaired the synthesis of sulfolipids in
E
.
histolytica
.
Conclusions/Significance
Hence, the combined approach of
in silico
and
in vitro
-based EhAPSK analyses identified compounds that can be evaluated for their effects on
Entamoeba
. This can provide leads for the development of new anti-amoebic and amoebiasis transmission-blocking drugs. This strategy can also be applied to identify specific APSK inhibitors, which will benefit research into sulfur metabolism and the ubiquitous pathway terminally synthesizing essential sulfur-containing biomolecules.