The long-term objective of this application is to elucidate the roles of a novel group of proteins related in sequence and structure to catalase and to define the biochemistry and chemistry of their reactions and novel products. Catalase is renowned for its key role in the oxidative defense of all aerobic organisms. One can anticipate selective reactions of these new catalase relatives with potential oxidative metabolism and/or functioning in the disposition of natural peroxides. The prototypical enzyme of this proposal is an allene oxide synthase, an enzyme that catalyzes a cytochrome P450-type of reaction yet which exhibits distinct sequence homology to catalase.
In Aim 1, a newly available X-ray crystal structure of the catalase-related AOS will be used to reveal the mechanistic basis of catalysis and the comparisons and contrasts with human catalase. The goal is to provide an understanding of the ability to catalyze P450-type chemistry within the catalase fold.
Aim 2 will focus on analysis of the catalytic activities of other novel enzyme candidates that have similar sequence characteristics defined as retention of the heme-binding features of a catalase within an unusually short polypeptide for catalases of only ~40kD. These enzymes occur in organisms that include bacteria of importance for their pathogenicity and a crop blight fungus characterized as a major threat to the world's food supply. Allene oxides are of major importance in biotechnology and their cyclopentenone derivatives are also studied for their potent antineoplastic effects.
Aim 3 will seek to establish the structure and precise stereochemistry of natural allene oxides and especially structural issues pertinent to their cyclizations. This is of fundamental interest in understanding the nature of allene oxide synthase reactions as well as the chemistry of cyclopentenone synthesis. The results of this study will provide new insights and a new way of thinking about the enzymatic capabilities of a long-recognized protein family with established roles as a sentinel at the forefront of oxidative defense. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM074888-02
Application #
7208012
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Ikeda, Richard A
Project Start
2006-04-01
Project End
2010-03-31
Budget Start
2007-04-01
Budget End
2008-03-31
Support Year
2
Fiscal Year
2007
Total Cost
$282,962
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Pharmacology
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37212
Teder, Tarvi; Boeglin, William E; Brash, Alan R (2017) Oxidation of C18 Hydroxy-Polyunsaturated Fatty Acids to Epoxide or Ketone by Catalase-Related Hemoproteins Activated with Iodosylbenzene. Lipids 52:587-597
Hebert, Sebastien P; Cha, Jin K; Brash, Alan R et al. (2016) Investigation into 9(S)-HPODE-derived allene oxide to cyclopentenone cyclization mechanism via diradical oxyallyl intermediates. Org Biomol Chem 14:3544-57
Mashhadi, Zahra; Newcomer, Marcia E; Brash, Alan R (2016) The Thr-His Connection on the Distal Heme of Catalase-Related Hemoproteins: A Hallmark of Reaction with Fatty Acid Hydroperoxides. Chembiochem 17:2000-2006
Mashhadi, Zahra; Boeglin, William E; Brash, Alan R (2015) Robust inhibitory effects of conjugated linolenic acids on a cyclooxygenase-related linoleate 10S-dioxygenase: Comparison with COX-1 and COX-2. Biochim Biophys Acta 1851:1346-52
Teder, Tarvi; Lõhelaid, Helike; Boeglin, William E et al. (2015) A Catalase-related Hemoprotein in Coral Is Specialized for Synthesis of Short-chain Aldehydes: DISCOVERY OF P450-TYPE HYDROPEROXIDE LYASE ACTIVITY IN A CATALASE. J Biol Chem 290:19823-32
Mashhadi, Zahra; Boeglin, William E; Brash, Alan R (2014) Inhibitory effects of a novel Val to Thr mutation on the distal heme of human catalase. Biochimie 106:180-3
Brash, Alan R; Niraula, Narayan P; Boeglin, William E et al. (2014) An ancient relative of cyclooxygenase in cyanobacteria is a linoleate 10S-dioxygenase that works in tandem with a catalase-related protein with specific 10S-hydroperoxide lyase activity. J Biol Chem 289:13101-11
Teder, Tarvi; Boeglin, William E; Brash, Alan R (2014) Lipoxygenase-catalyzed transformation of epoxy fatty acids to hydroxy-endoperoxides: a potential P450 and lipoxygenase interaction. J Lipid Res 55:2587-96
Brash, Alan R; Boeglin, William E; Stec, Donald F et al. (2013) Isolation and characterization of two geometric allene oxide isomers synthesized from 9S-hydroperoxylinoleic acid by cytochrome P450 CYP74C3: stereochemical assignment of natural fatty acid allene oxides. J Biol Chem 288:20797-806
Jin, Jing; Boeglin, William E; Cha, Jin K et al. (2012) 8R-Lipoxygenase-catalyzed synthesis of a prominent cis-epoxyalcohol from dihomo-?-linolenic acid: a distinctive transformation compared with S-lipoxygenases. J Lipid Res 53:292-9

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