Transformation of AA to 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

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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