Difference between revisions of "Transformation of AA to 12-HPETE"

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[[Welcome to the In-Silico Model of Cutaneous Lipids Wiki | Return to overview]]
 
[[Welcome to the In-Silico Model of Cutaneous Lipids Wiki | Return to overview]]
  
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LOX enzymes oxidise AA to generate hydroxy fatty acids. In the skin, the 12-LOX isoform of LOX is more active than others. This isoform is highly expressed in the resident cells of both compartments, epidermal keratinocytes and dermal fibroblasts (Dowd, Kobza Black et al. 1985). The 12- LOX enzyme catalyses the addition of O2 at the C-12 position of AA, producing 12-HPETE.
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The 12- LOX enzyme catalyses the addition of O2 at the C-12 position of AA, producing 12-HPETE. The formation of the unstable hydroperoxy fatty acids (HPETE) begins with the abstraction of a hydrogen radical at the allylic position between two double bonds. The structure undergoes a rearrangement reaction which results in the formation of a conjugated diene system. The insertion of molecular oxygen and a hydrogen leads to the formation of the final structure, a hydroperoxy fatty acid.  
  
 
== Reaction ==
 
== Reaction ==

Latest revision as of 09:18, 21 August 2019

Return to overview

The 12- LOX enzyme catalyses the addition of O2 at the C-12 position of AA, producing 12-HPETE. The formation of the unstable hydroperoxy fatty acids (HPETE) begins with the abstraction of a hydrogen radical at the allylic position between two double bonds. The structure undergoes a rearrangement reaction which results in the formation of a conjugated diene system. The insertion of molecular oxygen and a hydrogen leads to the formation of the final structure, a hydroperoxy fatty acid.

Reaction

R179AA - HPETE12.jpg

Chemical equation

AA \rightleftharpoons 12-HPETE

Rate equation

R19.PNG

Enzyme Parameters

Kms

Literature values
Value Units Species Notes Weight Reference
7.20E-03 mM Human Expression Vector: Platelet

Enzyme: 12-Lipoxygenase pH: 7.4 Temperature: 37°C.

2048 [1]
8.00E-02 mM Human Expression Vector: Platelet

Enzyme: 12-Lipoxygenase pH: 7 Temperature: 24

512 [2]
1.00E-02 mM Human Platlet Expression Vector: Baculovirus

Enzyme: 12-Lipoxygenase pH: 8 Temperature: 37

256 [3]
7.90E-03 ± 8.00E-04 mM Human Expression Vector: Platelets

Enzyme:12-Lipoxygenase pH: 7.4 Temperature: 37

2048 [4]
Description of the 12-LOX Kms distribution
Mode (mM) Confidence Interval Location parameter (σ) Scale parameter (σ)
7.60E-03 4.34E+00 -4.48E+00 6.30E-01
The estimated probability distribution for 12-LOX 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 12-LOX Kmp distribution
Mode (mM) Location parameter (µ) Scale parameter (σ)
7.30E-03 -4.52E+00 6.28E-01
The estimated probability distribution for 12-LOX 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
336 ± 12 per minute Human Expression Vector: Human reticulocyte

Enzyme: 15-lipoxygenase-1 pH: 7.5 Temperature: 25

256 [5]
504 per minute Wild Boar Expression Vector: E. coli.

Enzyme: 12-Lipoxygenase pH: 7.4 Temperature: 37

1024 [6]
Description of the 12-LOX kcat distribution
Mode (min-1) Confidence Interval Location parameter (µ) Scale parameter (σ)
4.87E+02 1.20E+00 6.22E+00 1.80E-01
The estimated probability distribution for 12-LOX 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.

12-LOX Abundance
Value Units Species Notes Weight Reference
19.8 ppm Human Expression Vector: Spleen

Enzyme: 12-LOX pH: 7.5 Temperature: 37 °C

1024 [7]
1.60 ppm Human Expression Vector: Liver

Enzyme: 12-LOX pH: 7.5 Temperature: 37 °C

1024 [8]
0.28 ppm Human Expression Vector: Gut

Enzyme: 12-LOX pH: 7.5 Temperature: 37 °C

1024 [8]
0.11 ppm Human Expression Vector: Pancreas

Enzyme: 12-LOX pH: 7.5 Temperature: 37 °C

1024 [8]
Description of the 12-LOX concentration distribution
Mode (ppm) Mode (mM) Confidence Interval Location parameter (µ) Scale parameter (σ)
4.98E-01 2.76E-06 7.23E+00 7.12E-01 1.19E+00
The estimated probability distribution for 12-LOX 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 Change Units Species Notes Weight Reference
(-69.979996) kcal/mol Not stated Estimated

Enzyme: 12-LOX Substrate: Arachidonate Product: 12-HPETE pH: 7.3 ionic strength: 0.25

64 [9]
Description of the 12-LOX Keq distribution
Mode Confidence Interval Location parameter (µ) Scale parameter (σ)
2.27E+51 1.00E+01 1.19E+02 8.90E-01
The estimated probability distribution for 12-LOX 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. ↑ Lagarde M. "Subcellular localization and some properties of lipoxygenase activity in human blood platelets. Biochem J. 1984 Sep 1;222(2):495-500.
  2. ↑ Hada T. "Catalytic properties of human platelet 12-lipoxygenase as compared with the enzymes of other origins. Biochim Biophys Acta. 1991 Apr 24;1083(1):89-93.
  3. ↑ Chen X. S. "Purification and characterization of recombinant histidine-tagged human platelet 12-lipoxygenase expressed in a baculovirus/insect cell system. Eur J Biochem. 1993 Jun 15;214(3):845-52.
  4. ↑ Romano M. "Lipoxin synthase activity of human platelet 12-lipoxygenase. Biochem J. 1993 Nov 15;296 ( Pt 1):127-33.
  5. ↑ [www.ncbi.nlm.nih.gov/pubmed/19469483 Wecksler A. "Mechanistic Investigations of Human Reticulocyte 15- and Platelet 12-Lipoxygenases with Arachidonic Acid Biochemistry, 2009, 48 (26), pp 6259–6267]
  6. ↑ Richards K. "Leukocyte 12-Lipoxygenase:  Expression, Purification, and Investigation of the Role of Methionine Residues in Turnover-Dependent Inactivation and 5,8,11,14-Eicosatetraynoic Acid Inhibition Biochemistry, 1997, 36 (22), pp 6692–6699
  7. ↑ M. Wilhelm Mass-spectrometry-based draft of the human proteome Nature, 2014 509, 582–587
  8. ↑ 8.0 8.1 8.2 M. Kim A draft map of the human proteome Nature, 2014 509, 575–581
  9. ↑ 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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