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Thromboxane synthase inhibitors inhibit the final enzyme (thromboxane synthase) in the synthesis of thromboxane. Ifetroban is a potent and selective thromboxane receptor antagonist. [ 10 ] Dipyridamole antagonizes this receptor too, but has various other mechanisms of antiplatelet activity as well.
The human thromboxane A (TXA) synthase is a 60 kDa cytochrome P450 protein with 533 amino acids and a heme prosthetic group. This enzyme, anchored to the endoplasmic reticulum, is found in platelets, monocytes, and several other cell types. The NH2 terminus contains two hydrophobic segments whose secondary structure is believed to be helical.
Prostacyclin is produced in endothelial cells, which line the walls of arteries and veins, [14] from prostaglandin H 2 (PGH 2) by the action of the enzyme prostacyclin synthase. Although prostacyclin is considered an independent mediator, it is called PGI 2 (prostaglandin I 2 ) in eicosanoid nomenclature, and is a member of the prostanoids ...
Activation of TP receptors stimulates vascular endothelial cell pro-inflammatory responses such as increased expression of cell surface adhesion proteins (i.e. ICAM-1, VCAM-1, and E-selectin); stimulates apoptosis (i.e. cell death) of CD4+ and CD8+ lymphocytes; causes the chemokinesis (i.e. cell movement) of native T cells; and impairs the ...
The endothelium (pl.: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. [1] The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall.
Thromboxane A 2 (TXA 2) is generated from prostaglandin H 2 by thromboxane-A synthase in a metabolic reaction which generates approximately equal amounts of 12-hydroxyheptadecatrienoic acid (12-HHT). Aspirin irreversibly inhibits platelet cyclooxygenase 1 preventing the formation of prostaglandin H 2 , and therefore TXA 2 .
Thromboxane A2 (TX2) has a positive feedback in platelet activation. It is produced by the oxygenation of arachidonic acid by two enzymes: cycloxygenase and thromboxane A2 synthase. TX2 effects are mediated by G protein-coupled receptors, subtypes TPα and TPβ.
A thromboxane synthase has also been identified. Prostaglandin-F synthase (PGFS) catalyzes the formation of 9α,11β-PGF 2α,β from PGD 2 and PGF 2α from PGH 2 in the presence of NADPH. This enzyme has recently been crystallized in complex with PGD 2 [ 11 ] and bimatoprost [ 12 ] (a synthetic analogue of PGF 2α ).