MECHANISTIC DISSECTION OF ALTERNATIVE REACTIONS CATALYZED BY IRON(II)- AND 2-(OXO)GLUTARATE-DEPENDENT OXYGENASES

Open Access
Author:
Butch, Susan Elizabeth
Graduate Program:
Chemistry
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 05, 2016
Committee Members:
  • J. Martin Bollinger, Jr., Thesis Advisor
  • Carsten Krebs, Committee Member
  • Amie Kathleen Boal, Committee Member
Keywords:
  • carbapenem
  • oxygenases
Abstract:
Iron(II)- and 2-(oxo)glutarate-dependent (Fe/2OG) oxygenases catalyze an astonishing array of biochemical reactions with diverse and important physiological functions. Their manifold of primarily oxidative transformations arises from a conserved iron(IV)-oxo (ferryl) intermediate that forms upon the coupled activation of O2 and decarboxylation of 2OG to succinate at the iron cofactor. In well-understood transformations of sp3-hybridized carbon centers, the ferryl intermediate abstracts a hydrogen atom (H•); the most common outcome, hydroxylation, then results from coupling (often termed "rebound") between the OH ligand and substrate radical produced by the H•-transfer (HAT) step. This investigation explores the alternative outcomes effected by two Fe/2OG enzymes: xanthine:2OG dioxygenase, XanA, which hydroxylates an sp2-hybridized carbon (C8) of xanthine to produce uric acid, and carbapenem synthase, CarC, which effects sequential redox-neutral (with respect to the substrate) epimerization and 1,2-dehydrogenation reactions. Members of this enzyme family could be used combinatorially for the construction of new drug compounds, but only with a fundamental understanding of how individual members direct different types of reactivity can we optimally exploit them for such a purpose.