The cyclooxygenase activity of prostaglandin H synthase (PGHS) catalyzes the first committed step in the biosynthesis of the prostaglandins, a group of potent, bioactive lipids believed important in many pathophysiological processes, including inflammation, vascular, gastric and renal function, reproduction, and tumorigenesis. Two PGHS isoforms are known: PGHS-1 is regarded as constitutive and is ascribed housekeeping function; PGHS 2 is strongly inducible by cytokines in many cells involved in inflammatory and proliferative processes. Besides the controls of PGHS- 1 and -2 gene expression, cellular prostaglandin synthesis is also tightly regulated at the cyclooxygenase catalytic level, with different catalytic controls for the two PGHS isoforms. PGHS-2 cyclooxygenase has a much lower hydroperoxide activator requirement than the PGHS-1 cyclooxygenase. This difference in feedback activation by the product provides a simple biochemical basis for differential cellular control of cyclooxygenase catalysis. Cellular cyclooxygenase catalysis also can be limited by fatty acid substrate availability. PGHS-1 cyclooxygenase activity exhibits cooperative behavior at low arachidonic acid levels, whereas the PGHS-2 enzyme follows simple saturable kinetics. The general goal of this project is to understand the regulation of catalysis by the PGHS isoforms at a molecular level. Kinetic, spectroscopic, and structural studies will be undertaken with the two PGHS isoforms and targeted mutant proteins to achieve the following specific aims: 1) Identify the mechanistic basis(es) for the different hydroperoxide activator requirements in PGHS-1 and -2, and investigate the mechanistic changes in aspirin-treated PGHS-2; 2) Identify the structural element(s) controlling the hydroperoxide activator requirements in PGHS-1 and -2, and investigate the mechanistic changes in aspirin-treated PGHS-2; 2) Identify the structural element(s) controlling the hydroperoxide activator requirements in the two isoforms; and 3) Evaluate the interdependence between fatty acid and peroxide in cyclooxygenase catalytic control for the two PGHS isoforms.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM052170-05
Application #
2697720
Study Section
Medical Biochemistry Study Section (MEDB)
Project Start
1994-12-01
Project End
2002-11-30
Budget Start
1998-12-01
Budget End
1999-11-30
Support Year
5
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of Texas Health Science Center Houston
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
City
Houston
State
TX
Country
United States
Zip Code
77225
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Wu, Gang; Lu, Jian-Ming; van der Donk, Wilfred A et al. (2011) Cyclooxygenase reaction mechanism of prostaglandin H synthase from deuterium kinetic isotope effects. J Inorg Biochem 105:382-90
Tsai, Ah-lim; Wu, Gang; Rogge, Corina E et al. (2011) Structural comparisons of arachidonic acid-induced radicals formed by prostaglandin H synthase-1 and -2. J Inorg Biochem 105:366-74
Tsai, Ah-Lim; Kulmacz, Richard J (2010) Prostaglandin H synthase: resolved and unresolved mechanistic issues. Arch Biochem Biophys 493:103-24
Wu, Gang; Tsai, Ah-Lim; Kulmacz, Richard J (2009) Cyclooxygenase competitive inhibitors alter tyrosyl radical dynamics in prostaglandin H synthase-2. Biochemistry 48:11902-11
Rogge, Corina E; Liu, Wen; Kulmacz, Richard J et al. (2009) Peroxide-induced radical formation at TYR385 and TYR504 in human PGHS-1. J Inorg Biochem 103:912-22
Rand Doyen, J; Yucer, Nur; Lichtenberger, Lenard M et al. (2008) Phospholipid actions on PGHS-1 and -2 cyclooxygenase kinetics. Prostaglandins Other Lipid Mediat 85:134-43
Wu, Gang; Rogge, Corina E; Wang, Jinn-Shyan et al. (2007) Oxyferryl heme and not tyrosyl radical is the likely culprit in prostaglandin H synthase-1 peroxidase inactivation. Biochemistry 46:534-42
Liu, Wen; Cao, Dazhe; Oh, Sungwhan F et al. (2006) Divergent cyclooxygenase responses to fatty acid structure and peroxide level in fish and mammalian prostaglandin H synthases. FASEB J 20:1097-108
Liu, W; Wang, L-H; Fabian, P et al. (2006) Arabidopsis thaliana fatty acid alpha-dioxygenase-1: evaluation of substrates, inhibitors and amino-terminal function. Plant Physiol Biochem 44:284-93

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