Indiana University-Purdue University Indianapolis (IUPUI) / The human aldehyde dehydrogenase (ALDH) superfamily consists of 19 isoenzymes that
are critical for normal physiology as well as the removal of toxic aldehydes. Members of
the ALDH1/2 family have vital roles in cell signaling during early development, ethanol
metabolism, and the removal of aldehydes derived from oxidative stress. We sought to
develop selective compounds toward ALDH2 to help determine its individual
contribution to biological function, as many of the ALDH1/2 family possess overlapping
substrate preferences. A high-throughput screen of over 100,000 compounds uncovered a
class of aromatic lactones which inhibit the ALDH1/2 enzyme family. The lactones were
then characterized using a combination of enzyme kinetics, X-ray crystallography, and
cell culture experiments. We found that many of the lactones are over ten times more
potent toward ALDH2 than daidzin, a previously described ALDH2 inhibitor. Our ability
to produce many more ALDH isoenzymes allowed us to determine that daidzin is not as
selective as previously believed, inhibiting ALDH2, ALDH1B1, and ALDH1A2 with
equal potency. This inhibition pattern was seen with several of the aromatic lactones as
well. Structural studies show that many of the lactones bind between key aromatic
residues in the ALDH1/2 enzyme substrate-binding sites. One lactone in particular
mimics the position of an aldehyde substrate and alters the position of the catalytic cysteine to interfere with the productive binding of NAD+ for enzyme catalysis. Further
characterization of related compounds led to the realization that the mechanism of
inhibition, potency, and selectivity differs amongst the lactones based off the substituents
on the aromatic scaffold and its precise binding location. Two of these compounds were
found to be selective for one of the ALDH1/2 family members, BUC22, selective for
ALDH1A1, and BUC27, selective for ALDH2. BUC22 demonstrates ten-fold selectivity
for ALDH1A1 over ALDH1A2 and does not inhibit the remaining ALDH1/2 enzymes.
Additionally, treatment with BUC22 led to decreased growth of triple-negative breast
cancer cells in culture. BUC27 inhibits ALDH2 with the same potency as daidzin. Both
BUC22 and BUC27 could be further developed to use as chemical tools to better
understand the functional roles of ALDH1A1 and ALDH2 in biological systems.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/11777 |
| Date | 01 September 2016 |
| Creators | Buchman, Cameron D. |
| Contributors | Hurley, Thomas D., Elmendorf, Jeffrey S., Hoang, Quyen, Wek, Ronald C. |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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