Part:BBa_K5492200

Diamine oxidase - DAO

Codon optimised coding sequence of the diamine oxidase enyzme, improving on the part of iGEM20_SEHS-China BBa_K368002. The sequence was synthetised using adapter sequences from Twist Bioscience added to the 5' and 3' end of the part. The primers for this sequence can be found here: BBa_K5492010 BBa_K5492011

Usage and Biology

Diamine oxidase (DAO) is an enzyme present in mammals, which plays an important role in digestion, as it is essential for the extracellular metabolism of histamine. DAO oxidizes histamine, and the resulting Imidazole-4-acetoldehyde isn’t able to bind to histamine receptors, therefore limiting the biological activity of histamine. Limiting the level of histamine effect can be an appropriate approach in cases of inflammation, where you can anticipate the histamine level increase. On our skin this includes some chronic diseases such as psoriasis, but more often would be useful in handling the acute increase of histamine level, such as a wasp bite. The decrease in oral histamine administration may also help to prevent some acute GI inflammation and smoothing the symptoms of some chronic bowel diseases.

PCR – optimized DAO

We have found the following PCR protocol the most optimal for the part:

We added the following substrates in order: (each optimized and wild type)

We added the 6X DNA Loading dye to each PCR tubes. We loaded the wells of the gels with 12μL of DAO solution in the following order: 

1. D31O 2. D32O 3. D33O 4. D34O 5. Ladder 

Restriction – optimized DAO

We performed digestion of our sequences using EcoRI and BglII. Our protocol: We added the following substrates in order: The used green buffer contained the loading dye too.

Ligation

We added the following substrates in order:

Transformation

Protocol for the transformation of DH10B E. coli strain

1. For C2987H: Thaw a tube of NEB 5-alpha Competent E. coli cells on ice for 10 minutes.
2. Add 1-5 µl containing 1 pg-100 ng of plasmid DNA to the cell mixture. Carefully flick the tube 4-5 times to mix cells and DNA.
Do not vortex.
3. Place the mixture on ice for 30 minutes. Do not mix.
4. Heat shock at exactly 42°C for exactly 30 seconds. Do not mix.
5. Place on ice for 5 minutes. Do not mix.
6. Pipette 950 µl of room temperature SOC into the mixture.
7. Place at 37°C for 60 minutes. Shake vigorously (250 rpm) or rotate.
8. Warm selection plates to 37°C.
9. Mix the cells thoroughly by flicking the tube and inverting, then perform several 10-fold serial dilutions in SOC.
10. Spread 50-100 µl of each dilution onto a selection plate and incubate overnight at 37°C. 
Alternatively, incubate at 30°C for 24-36 hours or 25°C for 48 hours.

After transforming the DH10B E. coli strain using the heat shock method, bacterial colonies successfully grew on the antibiotic-containing culture medium.

ELISA

ELISA assay performed on HNMT/DAO proteins.

Table of measured absorbance at 450nm

A1-A8: Standard stock, in 2X serial dilution.
B1-B8 ; C1-C8; D1-D8: Capsuled enzyme with liposome, samples taken at different times.
E1-E8; F1-F8; G1-G8: Referential enzyme without liposome, samples taken at different times.
H1-H3: DAO in 1X; 5X; 10X dilution.

Assembly Compatibility:

• 10
  INCOMPATIBLE WITH RFC[10]

  Illegal PstI site found at 55
  
• 12
  INCOMPATIBLE WITH RFC[12]

  Illegal PstI site found at 55
  
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal BamHI site found at 1932
  Illegal BamHI site found at 2186
  Illegal XhoI site found at 802
  
• 23
  INCOMPATIBLE WITH RFC[23]

  Illegal PstI site found at 55
  
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal PstI site found at 55
  
• 1000
  COMPATIBLE WITH RFC[1000]