Mechanistic Studies of Lipoxygenases Using Synthetic Substrate Analogues
Jacquot, Cyril
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https://hdl.handle.net/2142/72246
Description
Title
Mechanistic Studies of Lipoxygenases Using Synthetic Substrate Analogues
Author(s)
Jacquot, Cyril
Issue Date
2008
Doctoral Committee Chair(s)
van der Donk, Wilfred A.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Biochemistry
Chemistry, Organic
Abstract
Lipid peroxidation plays a key role in the biochemistry of living systems. The oxidation of polyunsaturated fatty acids is crucial in pain and inflammation mediation, as well as in cardiovascular, gastrointestinal and reproductive function modulation. However, if excessively stimulated, this process leads to oxidative stress and pathologies such as cancer, atherosclerosis or Alzheimer's disease. Lipoxygenases are one of two enzyme classes that catalyze the first committed steps in the lipid peroxidation pathway.
Numerous mechanistic and structural studies have been performed with lipoxygenases, but two important aspects remain unresolved. First, due to the lack of solved structures of complexes of lipoxygenases and substrates or substrate analogues, no clear picture of the interaction between substrate and active-site residues is available. Secondly, mechanistic investigations have so far focused on the reactions of the enzymes with linoleic acid as a substrate since analogues are more readily available. However, the therapeutically important human enzymes process arachidonic acid predominantly under physiological conditions.
Herein are described the syntheses of sulfur-containing fatty acid analogues, which were found to inhibit lipoxygenases in kinetic assays. Studies of the enzymes with site-specifically deuterated arachidonic acid analogues are also reported. These led to the discovery of isotope-sensitive branching in the reactions of human lipoxygenases. In addition, the nature of the rate-limiting steps in the oxidation of arachidonic acid with lipoxygenases was determined. This information provided a means of comparison of the enzyme mechanism with arachidonic acid as substrate instead of linoleic acid.
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