Transformation of PGH2 to PGF2α

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The isomerisation of PGH2 to PGF2α is performed by PGFS. This reaction results in the formation of two hydroxyl groups at C9 and C11. Two isoforms of PGFS have been reported in the literature in humans, the aldo-keto reductase family 1-member C3 isoform (encoded by the AKR1C3 gene) and the prostamide/prostaglandin F synthase isoform (encoded by the PRXL2B gene).


Reaction

R3 PGH2 -PGF2A.jpg

Chemical equation

PGH2 \rightleftharpoons PGF2a

Rate equation

R03.PNG

Enzyme Parameters

Kms

Literature values
Value Units Species Notes Weight Reference
1.90E-03 ± 1.5E-03 mM Human Placental Aldose Reductase (AKR1B1), E. Coli, pH 7, 37°C 512 [1]
1.80E-02 mM Human Lung PGF2a Synthase (AKR1C3), E. Coli, pH 7, 37°C 512 [1]
Description of the PGFS Kms distribution
Mode (mM) Confidence Interval Location parameter (µ) Scale parameter (σ)
1.33E-02 3.81E+00 -3.45E+00 9.33E-01
The estimated probability distribution for PGFS 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.

Kmp

This is a “Dependent parameter”, meaning that the log-normal distribution for this parameter was calculated using multivariate distributions (this is discussed in detail here). As a result, no confidence interval factor or literature values were cited for this parameter.

Description of the PGFS Kmp distribution
Mode (mM) Location parameter (µ) Scale parameter (σ)
1.46E-02 -2.86E+00 1.17E+00
The estimated probability distribution for PGFS 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.

kcat

Literature values
Value Units Species Notes Weight Reference
14.9 per minute Mouse/Swine Prostamide/PGF Synthase Purified

from Swine Brain and of Murine Enzyme Expressed in E. coli

128 [2]
Description of the PGFS kcat distribution
Mode (min-1) Confidence Interval Location parameter (µ) Scale parameter (σ)
1.48E+01 1.10E+00 2.71E+00 9.49E-02
The estimated probability distribution for PGFS 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
105 ppm Human Expression Vector: Platelet

Enzyme: PGFS pH: 7.5 Temperature: 37 °C

1024 [3]
19.9 ppm Human Expression Vector: Lung

Enzyme: PGFS pH: 7.5 Temperature: 37 °C

1024 [4]
40.3 ppm Human Expression Vector: Esophagus

Enzyme: PGFS pH: 7.5 Temperature: 37 °C

1024 [4]
110 ppm Human Expression Vector: Oral Cavity

Enzyme: PGFS pH: 7.5 Temperature: 37 °C

1024 [4]
Description of the PGFS concentration distribution
Mode (ppm) Mode (mM) Confidence Interval Location parameter (µ) Scale parameter (σ)
6.41E+01 3.55E-04 2.05E+00 4.53E+00 6.06E-01


The estimated probability distribution for PGFS 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.

Keq

Gibbs Free Energy Change
Value Units Species Notes Weight Reference
(-6.64) kcal/mol Not stated Estimated

Enzyme: PGFS Substrate: Arachidonate Product: PGF2a pH: 7.3 ionic strength: 0.25

64 [5]
Mode Confidence Interval Location parameter (µ) Scale parameter (σ)
7.46E+04 1.00E+01 1.20E+01 8.90E-01
The estimated probability distribution for PGFS Keq. 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.

References

  1. ↑ 1.0 1.1 Z. Kabututu, M. Manin, Prostaglandin F2alpha synthase activities of aldo-keto reductase 1B1, 1B3 and 1B7. J Biochem 2009,145(2):161-8)
  2. ↑ Moriuchi H., Molecular characterization of a novel type of prostamide/prostaglandin F synthase, belonging to the thioredoxin-like superfamily. J Biol Chem. 2008 Jan 11;283(2):792-801.)
  3. ↑ M. Kim A draft map of the human proteome Nature, 2014 509, 575–581
  4. ↑ 4.0 4.1 4.2 M. Wilhelm Mass-spectrometry-based draft of the human proteome Nature, 2014 509, 582–587
  5. ↑ Caspi et al 2014, "The MetaCyc database of metabolic pathways and enzymes and the BioCyc collection of Pathway/Genome Databases," Nucleic Acids Research 42:D459-D471


Related Reactions

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