Elucidating Substrate Promiscuity within the FabI Enzyme Family

The rapidly growing
appreciation of enzymes’ catalytic and
substrate promiscuity may lead to their expanded use in the fields
of chemical synthesis and industrial biotechnology. Here, we explore
the substrate promiscuity of enoyl-acyl carrier protein reductases
(commonly known as FabI) and how that promiscuity is a function of
inherent reactivity and the geometric demands of the enzyme’s
active site. We demonstrate that these enzymes catalyze the reduction
of a wide range of substrates, particularly α,β-unsaturated
aldehydes. In addition, we demonstrate that a combination of quantum
mechanical hydride affinity calculations and molecular docking can
be used to rapidly categorize compounds that FabI can use as substrates.
The results here provide new insight into the determinants of catalysis
for FabI and set the stage for the development of a new assay for
drug discovery, organic synthesis, and novel biocatalysts.