Iron-dependent non-heme oxygenases are the specific focus of this research. These enzymes catalyze vital metabolic and catabolic reactions throughout mammalian metabolism. The initial intent is to develop a fundamental understanding of the chemistry of these enzymes by the identification of the transient oxygen intermediates that are generated during catalysis. The long-term objective is to find evidence for the geometry of transition states for specific catalytic steps such that stable transition state mimics can be developed as inhibitory therapeutic agents to control the flux through key metabolic pathways. Initially, the enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD) has been selected for investigation. This enzyme exemplifies many of the catalytic functions of other FeII-dependent non-heme dioxygenases such as aromatic oxygenation, oxidative decarboxylation and substituent migration. Furthermore, it is one of the few alpha-keto acid-dependent oxygenases for which the crystal structure is known. Moreover, it has become a paradigm example of the ability to alleviate metabolic disorders through selective enzymatic inhibition. Type 1 Tyrosinemia, is caused by a deficiency of active fumarylacetoacetase, an enzyme that catalyzes the final step in the pathway for the catabolism of tyrosine. In the absence of treatment this disease is often fatal in the first year of life and always prior the completion of the first two decades. It is known, however, that the inhibition of HPPD which catalyzes the second step of this pathway is, in most cases, an effective treatment for type 1 Tyrosinemia. Part of the intent of this research is that the mechanism of this inhibition be understood in the context of catalytic events of the enzyme. The experimental approach will be to combine steady state and pre-steady state analyses with the selective use of substrate analogs, isotopic labels and mutagenesis and crystallography to test mechanistic hypotheses on the basis of rate constant modulation and structure.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK059551-02
Application #
6624213
Study Section
Biochemistry Study Section (BIO)
Program Officer
Sechi, Salvatore
Project Start
2002-04-15
Project End
2006-02-28
Budget Start
2003-04-01
Budget End
2004-02-29
Support Year
2
Fiscal Year
2003
Total Cost
$197,845
Indirect Cost
Name
University of Wisconsin Milwaukee
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
627906399
City
Milwaukee
State
WI
Country
United States
Zip Code
53201
Brownlee, June; He, Panqing; Moran, Graham R et al. (2008) Two roads diverged: the structure of hydroxymandelate synthase from Amycolatopsis orientalis in complex with 4-hydroxymandelate. Biochemistry 47:2002-13
Conrad, John A; Moran, Graham R (2008) The Interaction of Hydroxymandelate Synthase with the 4-Hydroxyphenylpyruvate Dioxygenase Inhibitor: NTBC. Inorganica Chim Acta 361:1197-1201
Neidig, Michael L; Brown, Christina D; Kavana, Michael et al. (2006) Spectroscopic and electronic structure studies of the role of active site interactions in the decarboxylation reaction of alpha-keto acid-dependent dioxygenases. J Inorg Biochem 100:2108-16
Neidig, Michael L; Decker, Andrea; Choroba, Oliver W et al. (2006) Spectroscopic and electronic structure studies of aromatic electrophilic attack and hydrogen-atom abstraction by non-heme iron enzymes. Proc Natl Acad Sci U S A 103:12966-73
Purpero, Vincent M; Moran, Graham R (2006) Catalytic, noncatalytic, and inhibitory phenomena: kinetic analysis of (4-hydroxyphenyl)pyruvate dioxygenase from Arabidopsis thaliana. Biochemistry 45:6044-55
Johnson-Winters, Kayunta; Purpero, Vincent M; Kavana, Michael et al. (2005) Accumulation of multiple intermediates in the catalytic cycle of (4-hydroxyphenyl)pyruvate dioxygenase from Streptomyces avermitilis. Biochemistry 44:7189-99
Moran, Graham R (2005) 4-Hydroxyphenylpyruvate dioxygenase. Arch Biochem Biophys 433:117-28
Neidig, Michael L; Decker, Andrea; Kavana, Michael et al. (2005) Spectroscopic and computational studies of NTBC bound to the non-heme iron enzyme (4-hydroxyphenyl)pyruvate dioxygenase: active site contributions to drug inhibition. Biochem Biophys Res Commun 338:206-14
Brownlee, June M; Johnson-Winters, Kayunta; Harrison, David H T et al. (2004) Structure of the ferrous form of (4-hydroxyphenyl)pyruvate dioxygenase from Streptomyces avermitilis in complex with the therapeutic herbicide, NTBC. Biochemistry 43:6370-7
Neidig, Michael L; Kavana, Michael; Moran, Graham R et al. (2004) CD and MCD studies of the non-heme ferrous active site in (4-hydroxyphenyl)pyruvate dioxygenase: correlation between oxygen activation in the extradiol and alpha-KG-dependent dioxygenases. J Am Chem Soc 126:4486-7

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