Transformation of 15-Keto-PGE2 to 13,14-Dihydro-15-Keto-PGE2

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The second step of the catabolic pathway of prostanoids is the reduction of the conjugated α, β-unsaturated double bond at C13, by 13, 15-ketoprostglandin reductase, also known as prostaglandin reductase. There are two isoforms of this protein, prostaglandin reductase 1 (PTGR-1) and prostaglandin reductase 2 (PTGR-2). Prostaglandin reductase 1 (PTGR-1) can accept a wide variety of prostaglandins as substrates. Prostaglandin reductase 2 (PTGR-2) has the highest affinity for 15-keto-PGE2, but also accepts a wide variety of prostaglandins as a substrate [1].

Reaction

Chemical equation

15-Keto-PGE2 + NAD(P)+ \rightleftharpoons 13,14-Dihydro-15-Keto-PGE2 + NAD(P)H

Rate equation

R69.PNG

Parameters

Kms

Literature values
Value Units Species Notes Weight Reference
0.01121 ± 0.00014 mM Human Method: In vitro

Organism: Human Expression vector: E.coli Enzyme: PTGR2 pH: 7.5 Temperature: 37 ◦C Substrate: 15-Keto-PGE2

"For determining the KM and Vmax values for NADPH, 15-keto-PGE2 at a final concentration of 200 mM was used with different concentrations of NADPH (0–60 mM)."

512 [2]
0.01587 ± 0.00171 mM Human Method: In vitro

Organism: Human Expression vector: E.coli Enzyme: e PTGR2 pH: 7.5 Temperature: 37 ◦C Substrate: NADPH

"For determining the KM and Vmax values for NADPH, 15-keto-PGE2 at a final concentration of 200 mM was used with different concentrations of NADPH (0–60 mM)."

512 [2]


Description of the PTGR-2 Kms distribution
Mode (mM) Confidence Interval Location parameter (µ) Scale parameter (σ)
1.20E-02 4.92E+00 -3.97E+00 6.71E-01
The estimated probability distribution for PTGR-2 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

Description of the PTGR-2 Kmp distribution
Mode (mM) Location parameter (µ) Scale parameter (σ)
1.19E-02 -3.97E+00 6.81E-01
The estimated probability distribution for PTGR-2 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

Note: Turnover values from EC 1.3.1.48 - 13,14-dehydro-15-oxoprostaglandin 13-reductase

Literature values
Value Units Species Notes Weight Reference
11.4 ± 0.9 min-1 Mouse Method: In vitro

Organism: Mouse Expression vector: Enzyme: 13,14-dehydro-15-oxoprostaglandin 13-reductase pH: 7.4 Temperature: 37 ◦C Substrate: 15-Ketoprostaglandin E2

384 [2]
Description of the PTGR-2 kcat distribution
Mode (min-1) Confidence Interval Location parameter (µ) Scale parameter (σ)
1.14E+01 9.86E+00 3.22E+00 8.87E-01
The estimated probability distribution for PTGR-2 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
162 ppm Human Expression Vector: Skin

Enzyme: PTGR2 pH: 7.5 Temperature: 37 °C

2048 [3]
80.9 ppm Human Expression Vector: Skin

Enzyme: PTGR2 pH: Unknown Temperature: Unknown

2048 Unknown
74.1 ppm Human Expression Vector: Oral Cavity

Enzyme: PTGR2 pH: 7.5 Temperature: 37 °C

1024 [3]
Description of the PTGR-2 concentration distribution
Mode (ppm) Mode (mM) Confidence Interval Location parameter (µ) Scale parameter (σ)
8.65E+01 4.79E-04 1.45E+00 4.58E+00 3.47E-01
The estimated probability distribution for PTGR-2 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

Literature values
Gibbs Free energy Units Species Notes Weight Reference
3.6006165 kcal/mol Unspecified Calculations with a Gaussian98 suite of programs

Enzyme: COX (Unspecific) Substrate: Arachidonate Temperature: 298.15 K Pressure: 1 bar

64 [4]
Description of the PTGR-2 Keq distribution
Mode Confidence Interval Location parameter (µ) Scale parameter (σ)
2.28E-03 1.00E+01 -5.29E+00 8.91E-01
The estimated probability distribution for PTGR-2 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.

Misch

Half Life
Value Units Species Notes Reference
9.9 +/-0.2 minutes Dog In vivo

Temperature:37 pH:7

[5]
Vmax
Value Units Species Notes Reference
159.23 ± 0.71 nmol min-1 mg-1 Human Method: In vitro

Organism: Human Expression vector: E.coli Enzyme: PTGR2 pH: 7.5 Temperature: 37 ◦C Substrate: 15-Keto-PGE2

[2]
66.73 ± 1.36 nmol min-1 mg-1 Human Method: In vitro

Organism: Human Expression vector: E.coli Enzyme: PTGR2 pH: 7.5 Temperature: 37 ◦C Substrate: NADPH

[2]

References

  1. ↑ Wu, Yu-Hauh Ko, Tzu-Ping Guo, Rey-Ting Hu, Su-Ming Chuang, Lee-Ming Wang, Andrew H J., Structural basis for catalytic and inhibitory mechanisms of human prostaglandin reductase PTGR2,Structure (2008), 16, 1714-1723.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 "Structural basis for catalytic and inhibitory mechanisms of human prostaglandin reductase PTGR2", Structure. 2008 Nov 12;16(11):1714-23. doi: 10.1016/j.str.2008.09.007.
  3. ↑ 3.0 3.1 [http://www.nature.com/nature/journal/v509/n7502/pdf/nature13319.pdf M. Wilhelm Mass-spectrometry-based draft of the human proteome Nature, 2014 509, 582–587]
  4. ↑ P. Silva, "A theoretical study of radical-only and combined radical/carbocationic mechanisms of arachidonic acid cyclooxygenation by prostaglandin H synthase" Theor Chem Acc (2003) 110: 345
  5. ↑ W. Bothwell, "A radioimmunoassay for the unstable pulmonary metabolites of prostaglandin E1 and E2: an indirect index of their in vivo disposition and pharmacokinetics" Journal of Pharmacology and Experimental Therapeutics February 1982, 220 (2) 229-235
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