Many natural products contain cyclopropane, oxirane, or aziridine groups as key structural elements. These three-membered ring moieties are generally stable despite their considerable ring strain. However, the inherent reactivities of these small rings can be released by enzymatic activation. Such activation often leads to reactive intermediates that inhibit the corresponding enzyme, making these three-membered ring containing compounds potential drugs. Although these small ring structures have a long history as therapeutic agents and mechanistic probes, little is known about how they are constructed in nature. To explore the biosynthesis of these strained ring compounds and to facilitate drug design efforts, we have chosen to study several intriguing enzymes involved in oxirane and aziridine formation. These include (S)-2- hydroxypropylphosphonate epoxidase (HppE) and 2-hydroxyethylphosphonate methyltransferase (HepM) in the fosfomycin biosynthetic pathway, and the enzymes catalyzing aziridine ring formation in the azicemicin A biosynthetic pathway. These enzymes were selected for their significant biological roles, their novel catalytic mechanisms, and their potential as catalysts for the combinatorial biosynthesis of new therapeutics. The proposed experiments will address the following specific aims: (1) to investigate the catalytic mechanism of HppE, including the oxygen activation mechanism and the chemical nature of the reaction intermediates;(2) to characterize the catalytic properties of HepM, especially the functions of methylcobalamin and radical- SAM in catalysis, and the mechanism of the methylation reaction;(3) to establish the biosynthetic pathway of aziridine ring formation in azicemicin A, and to characterize the key enzymes involved in the transformation. These studies will not only lead to a better understanding of the catalytic mechanism of the targeted enzymes, but will also provide important insight for designing methods to control and mimic the catalytic functions of related enzymes, many of which are medically relevant. Our results are expected to contribute to the broad field of natural product biosynthesis and mechanistic enzymology, and may also assist future clinical applications for the development of new metabolites using pathway engineering and/or combinatorial biosynthetic methods.

Public Health Relevance

The objective of this application focuses on learning how oxygen and nitrogen containing three-membered ring compounds are biosynthesized and the mechanisms of the key enzymes involved. The insight gained from this work will be useful for the development of new small ring agents having therapeutic potential, and thus will have a positive impact on human health.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM040541-22
Application #
8117690
Study Section
Macromolecular Structure and Function E Study Section (MSFE)
Program Officer
Hagan, Ann A
Project Start
1989-04-01
Project End
2012-06-30
Budget Start
2011-07-01
Budget End
2012-06-30
Support Year
22
Fiscal Year
2011
Total Cost
$311,026
Indirect Cost
Name
University of Texas Austin
Department
Pharmacology
Type
Schools of Pharmacy
DUNS #
170230239
City
Austin
State
TX
Country
United States
Zip Code
78712
Thibodeaux, Christopher J; Liu, Hung-Wen (2017) The type II isopentenyl Diphosphate:Dimethylallyl diphosphate isomerase (IDI-2): A model for acid/base chemistry in flavoenzyme catalysis. Arch Biochem Biophys 632:47-58
Ko, Yeonjin; Wang, Shao-An; Ogasawara, Yasushi et al. (2017) Identification and Characterization of Enzymes Catalyzing Pyrazolopyrimidine Formation in the Biosynthesis of Formycin A. Org Lett 19:1426-1429
Lin, Chia-I; McCarty, Reid M; Liu, Hung-Wen (2017) The Enzymology of Organic Transformations: A Survey of Name Reactions in Biological Systems. Angew Chem Int Ed Engl 56:3446-3489
Patel, Ashay; Chen, Zhuo; Yang, Zhongyue et al. (2016) Dynamically Complex [6+4] and [4+2] Cycloadditions in the Biosynthesis of Spinosyn A. J Am Chem Soc 138:3631-4
Jackson, David R; Yu, Xia; Wang, Guojung et al. (2016) Insights into Complex Oxidation during BE-7585A Biosynthesis: Structural Determination and Analysis of the Polyketide Monooxygenase BexE. ACS Chem Biol 11:1137-47
Fage, Christopher D; Isiorho, Eta A; Liu, Yungnan et al. (2015) The structure of SpnF, a standalone enzyme that catalyzes [4 + 2] cycloaddition. Nat Chem Biol 11:256-8
Hashimoto, Takuya; Hashimoto, Junko; Teruya, Kuniko et al. (2015) Biosynthesis of versipelostatin: identification of an enzyme-catalyzed [4+2]-cycloaddition required for macrocyclization of spirotetronate-containing polyketides. J Am Chem Soc 137:572-5
Liu, Cheng-Hao; Wang, Shao-An; Ruszczycky, Mark W et al. (2015) Studies of 1-Amino-2,2-difluorocyclopropane-1-carboxylic Acid: Mechanism of Decomposition and Inhibition of 1-Aminocyclopropane-1-carboxylic Acid Deaminase. Org Lett 17:3342-5
Caldara-Festin, Grace; Jackson, David R; Barajas, Jesus F et al. (2015) Structural and functional analysis of two di-domain aromatase/cyclases from type II polyketide synthases. Proc Natl Acad Sci U S A 112:E6844-51
Kim, Hak Joong; Choi, Sei-hyun; Jeon, Byung-sun et al. (2014) Chemoenzymatic synthesis of spinosyn A. Angew Chem Int Ed Engl 53:13553-7

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