Transformation of PGH2 to TXA2

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PGH2 is synthesised into the TXs, TXA2 and TXB2, by TXAS. These species bind to the TP receptor and have been found to increase T-cell proliferation (Thomas, Rocha et al. 2003). However this species is found in low concentration in the cutaneous compartment, therefore it has been deduced that the species originates from infiltrating cells from the vascular system such as leukocytes and endothelial cells (Sugimoto, Arai et al. 2006).

Reaction

Chemical equation

$FA \rightleftharpoons AA$

Parameters

Michaelis-Menten Constants

Value	Units	Species	Notes	Reference
4.00E-03	$mM$	Human	Expression Vector: Human Monocyte Enzyme: Platelet Free Human Monocyte pH: 7.4 Temperature: 37
1.00E-02	$mM$	Human	Expression Vector: Human mirosome Enzyme: Human Thromboxane Synthase pH:7.4 Temperature:
2.20E-02	$mM$	Human	Expression Vector:Human platelet Enzyme: Human thromboxane synthase pH: 7.4 Temperature: 37

Enzyme Turnover Numbers

Value	Units	Species	Notes	Reference
2687	per minute	Human	Expression Vector: Human Platelets Enzyme: TXAS pH: 7.4 Temperature:30
1628	per minute	Human	Expression Vector:Platelet Microsomes Enzyme: TXAS pH:7.4 Temperature:37

TXAS Abundance

Value	Units	Species	Notes	Reference
949	$ppm$	Human	Expression Vector: Platelet Enzyme: TXAS pH: 7.5 Temperature: 37 °C
56.2	$ppm$	Human	Expression Vector: Lung Enzyme: TXAS pH: 7.5 Temperature: 37 °C
4.58	$ppm$	Human	Expression Vector: Urinary Bladder Enzyme: TXAS pH: 7.5 Temperature: 37 °C
101	$ppm$	Human	Expression Vector: Oral Cavity Enzyme: TXAS pH: 7.5 Temperature: 37 °C

Gibbs Free Energy Change

Value	Units	Species	Notes	Reference
41.08	kcal/mol	Not stated	Estimated Enzyme: TXAS Substrate: Arachidonate Product: TXA2 pH: 7.3 ionic strength: 0.25

Related Reactions

• Transformation of AA to PGH2
• Transformation of TXA2 to TXB2