Transformation of PGH2 to PGI2

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PGH2 is metabolised into the prostacyclin PGI2, by PGIS. This species has been associated with influencing the permeability of vascular compartment (Murata, Ushikubi et al. 1997). Similarly to the TX species, prostacyclins are only found in low concentration and are associated with infiltrating cells from the vascular compartment (Sugimoto, Arai et al. 2006).

Reaction

Chemical equation

$PGH2 \rightleftharpoons PGI2$

Rate equation

Parameters

K_ms

Literature values

Value	Units	Species	Notes	Weight	Reference
1.33E-02 ± 1.40E-03	$mM$	Human	Expression Vector: Bovine Endothelial and Aorta Cells Enzyme: Human PGIS pH:7.4 Temperature: 23	256
9.00E-03 ± 5.00E-03	$mM$	Bovine	Expression Vector: Bovine Endothelial and Aorta Cells Enzyme: Bovine PGIS pH:7.4 Temperature: 24	192

Description of the PGIS Kms distribution

Mode (mM)	Confidence Interval	Location parameter (µ)	Scale parameter (σ)
1.24E-02	2.46E+00	-4.22E+00	4.20E-01

The estimated probability distribution for PGIS Kms. The value and weight of the literature values used to define the distribution are indicated by an orange dashed line. The x axis is plotted on a log-scale.

K_mp

Description of the PGIS Kmp distribution

Mode (mM)	Location parameter (µ)	Scale parameter (σ)
1.29E-02	-4.182022605	0.414183521

The estimated probability distribution for PGIS Kmp. The value and weight of the literature values used to define the distribution are indicated by an orange dashed line. The x axis is plotted on a log-scale.

k_cat

Literature values

Value	Units	Species	Notes	Weight	Reference
147 ± 45	per minute	Cattle	Expression Vector: E. Coli Enzyme: Bovine PGIS pH:7.4 Temperature: 24	192

Description of the PGIS kcat distribution

Mode (min-1)	Confidence Interval	Location parameter (µ)	Scale parameter (σ)
1.41E+02	1.35E+00	5.028213628	0.287348692

The estimated probability distribution for PGIS kcat. The value and weight of the literature values used to define the distribution are indicated by an orange dashed line. The x axis is plotted on a log-scale.

Enzyme concentration

To convert the enzyme concentration from ppm to mM, the following equation was used.

Literature values

Value	Units	Species	Notes	Weight	Reference
412	$ppm$	Human	Expression Vector: Urinary bladder Enzyme: PGIS pH: 7.5 Temperature: 37 °C	1024
206	$ppm$	Human	Expression Vector: Lung Enzyme: PGIS pH: 7.5 Temperature: 37 °C	1024
60.1	$ppm$	Human	Expression Vector: Esophagus Enzyme: PGIS pH: 7.5 Temperature: 37 °C	1024
9.93	$ppm$	Human	Expression Vector: Oral Cavity Enzyme: PGIS pH: 7.5 Temperature: 37 °C	1024

Description of the PGIS concentration distribution

Mode (ppm)	Mode (mM)	Confidence Interval	Location parameter (µ)	Scale parameter (σ)
1.13E+02	6.25E-04	4.13E+00	5.67E+00	9.68E-01

The estimated probability distribution for PGIS concentration. The value and weight of the literature values used to define the distribution are indicated by an orange dashed line. The x axis is plotted on a log-scale.

K_eq

Literature values

Gibbs Free Energy Change	Units	Species	Notes	Weight	Reference
0.04	kcal/mol	Not stated	Estimated Enzyme: Transacylase Substrate: Product: pH: 7.3 ionic strength: 0.25	64

Description of the PGIS Keq distribution

Mode	Confidence Interval	Location parameter (µ)	Scale parameter (σ)
9.35E-01	1.00E+01	7.30E-01	8.90E-01

The estimated probability distribution for PGIS kcat. The value and weight of the literature values used to define the distribution are indicated by an orange dashed line. The x axis is plotted on a log-scale.

Related Reactions

• Transformation of AA to PGH2
• Transformation of PGI2 to 6-K-PGF1α