PDBsum entry 5ikq

Oxidoreductase

PDB id: 5ikq

Contents

Protein chains

551 a.a.

Ligands

NAG-NAG-MAN-MAN ×2

BOG

JMS ×2

NAG ×4

COH ×2

AKR ×3

Waters ×416

PDB id:

5ikq

Name:

Oxidoreductase

Title:

The structure of meclofenamic acid bound to human cyclooxygenase-2

Structure:

Prostaglandin g/h synthase 2. Chain: a, b. Synonym: cyclooxygenase-2,cox-2,phs ii,prostaglandin h2 synthase 2, pghs-2,prostaglandin-endoperoxide synthase 2. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: ptgs2, cox2. Expressed in: spodoptera frugiperda. Expression_system_taxid: 7108

Resolution:

2.41Å R-factor: 0.173 R-free: 0.212

Authors:

B.J.Orlando,M.G.Malkowski

Key ref:

B.J.Orlando and M.G.Malkowski (2016). Substrate-selective Inhibition of Cyclooxygeanse-2 by Fenamic Acid Derivatives Is Dependent on Peroxide Tone. J Biol Chem, 291, 15069-15081. PubMed id: 27226593 DOI: 10.1074/jbc.M116.725713

Date:

03-Mar-16 Release date: 25-May-16

Protein chains

P35354  (PGH2_HUMAN) -  Prostaglandin G/H synthase 2 from Homo sapiens

Seq: 604 a.a.

Struc: 551 a.a.

Enzyme reactions

• Enzyme class: E.C.1.14.99.1 - prostaglandin-endoperoxide synthase.
• Reaction: (5Z,8Z,11Z,14Z)-eicosatetraenoate + AH2 + 2 O2 = prostaglandin H2 + A + H2O

(5Z,8Z,11Z,14Z)-eicosatetraenoate + AH2 + 2 × O2 = prostaglandin H2 + + H2O (Bound ligand (Het Group name = COH) matches with 51.11% similarity)

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

Added reference

DOI no: 10.1074/jbc.M116.725713

J Biol Chem 291:15069-15081 (2016)

PubMed id: 27226593

Substrate-selective Inhibition of Cyclooxygeanse-2 by Fenamic Acid Derivatives Is Dependent on Peroxide Tone.

B.J.Orlando, M.G.Malkowski.

ABSTRACT

Cyclooxygenase-2 (COX-2) catalyzes the oxygenation of arachidonic acid (AA) and endocannabinoid substrates, placing the enzyme at a unique junction between the eicosanoid and endocannabinoid signaling pathways. COX-2 is a sequence homodimer, but the enzyme displays half-of-site reactivity, such that only one monomer of the dimer is active at a given time. Certain rapid reversible, competitive nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to inhibit COX-2 in a substrate-selective manner, with the binding of inhibitor to a single monomer sufficient to inhibit the oxygenation of endocannabinoids but not arachidonic acid. The underlying mechanism responsible for substrate-selective inhibition has remained elusive. We utilized structural and biophysical methods to evaluate flufenamic acid, meclofenamic acid, mefenamic acid, and tolfenamic acid for their ability to act as substrate-selective inhibitors. Crystal structures of each drug in complex with human COX-2 revealed that the inhibitor binds within the cyclooxygenase channel in an inverted orientation, with the carboxylate group interacting with Tyr-385 and Ser-530 at the top of the channel. Tryptophan fluorescence quenching, continuous-wave electron spin resonance, and UV-visible spectroscopy demonstrate that flufenamic acid, mefenamic acid, and tolfenamic acid are substrate-selective inhibitors that bind rapidly to COX-2, quench tyrosyl radicals, and reduce higher oxidation states of the heme moiety. Substrate-selective inhibition was attenuated by the addition of the lipid peroxide 15-hydroperoxyeicosatertaenoic acid. Collectively, these studies implicate peroxide tone as an important mechanistic component of substrate-selective inhibition by flufenamic acid, mefenamic acid, and tolfenamic acid.