Acetylcholinesterase (AChE) is an important enzyme and
target for
human therapeutics, environmental safety, and global food supply.
Inhibitors of this enzyme are also used for pest elimination and can
be misused for suicide or chemical warfare. Adverse effects of AChE
pesticides on nontarget organisms, such as fish, amphibians, and humans,
have also occurred as a result of biomagnifications of these toxic
compounds. We have exhaustively curated the public data for AChE inhibition
data and developed machine learning classification models for seven
different species. Each set of models were built using up to nine
different algorithms for each species and Morgan fingerprints (ECFP6)
with an activity cutoff of 1 μM. The human (4075 compounds)
and eel (5459 compounds) consensus models predicted AChE inhibition
activity using external test sets from literature data with 81% and
82% accuracy, respectively, while the reciprocal cross (76% and 82%
percent accuracy) was not species-specific. In addition, we also created
machine learning regression models for human and eel AChE inhibition
to return a predicted IC50 value for a queried molecule.
We did observe an improved species specificity in the regression models,
where a human support vector regression model of human AChE inhibition
(3652 compounds) predicted the IC50s of the human test
set to a better extent than the eel regression model (4930 compounds)
on the same test set, based on mean absolute percentage error (MAPE
= 9.73% vs 13.4%). The predictive power of these models certainly
benefits from increasing the chemical diversity of the training set,
as evidenced by expanding our human classification model by incorporating
data from the Tox21 library of compounds. Of the 10 compounds we tested
that were predicted active by this expanded model, two showed >80%
inhibition at 100 μM. This machine learning approach therefore
offers the ability to rapidly score massive libraries of molecules
against the models for AChE inhibition that can then be selected for
future in vitro testing to identify potential toxins.
It also enabled us to create a public website, MegaAChE, for single-molecule
predictions of AChE inhibition using these models at .