Team:Hong Kong UCCKE/Description
Where did our idea come from?
1% of the World’s population are suffering from gout and it is becoming more and more prevalent, solely in the U.S, 8.3 million people were affected. Our team’s PI’s family have been suffering from the disease for generations as well. As his students, and an iGEM team, we were inspired to find new detection methods and even a cure for gout.
What is Gout?
Gout is a form of arthritis due to elevated levels of uric acid in the blood. At high levels, uric acid crystallizes and accumulates in synovial fluid, causing massive pain, and a red, tender, hot, swollen joint.
The food we intake everyday contains purine, such as steak, organ meats and seafood etc.. The purines we intake will be catalyzed by several enzymes into uric acid (as shown on the pathway below). However, we, as homo sapiens lack uricase, as known as urate oxidase, which catalyzes uric acid into allantoin.
Normally, uric acid dissolves in your blood and passes through your kidneys into your urine. But sometimes your body either produces too much uric acid or your kidneys excrete too little uric acid. Since uric acid has a low solubility (0.6mg/100ml) in water, it may crystallize and deposit in your joints.
What is our plan?
There are three main sub-projects. We wish to detect patients’ gout symptoms, and to cure it by preventing excess uric acid from accumulating in the body. Several parts have been designed to achieve the above goals.
1.Blood uric acid level detector
Firstly, we hope to make a uric acid detector, which is Part BBa_K2197300. It encodes HucR, a repressor, and a GFP gene. Working with KRAB, a repressor enhancer, and hucO, an operative site for the above repressor, the first session of our part acts as a uric acid concentration sensitive promoter. The promoter controls the expression of GFP. Engineered e.coli encodes part BBa_K2197300. By adding blood samples to the culture medium of e.coli, e.coli expresses different levels of GFP. By measuring the GFP level with a plate reader, uric acid concentration of the sample can be estimated. This part ensures a rapid detection of uric acid concentration.
2.Uric acid decomposition
We wish to make an uric acid decomposer, Part BBa_K2197400. Having the same promoter, this cell produces urate oxidase, an enzyme that catalyses the oxidation of uric acid. First to 5-hydroxyisourate, then to allantoin
(Uric acid + O2 + H2O → 5-hydroxyisourate + H2O2
5-hydroxyisourate + H2O → allantoin + CO2)
But the human gene for urate oxidase is nonfunctional. In the future, we hope to make a capsule enclosing this engineered cell so that it can be taken in by patients and produce urate oxidase when it senses uric acid.
3. Uric acid transporter
We made a uric acid transporter, YgfU, which is an imitation of Glut9. Glut9, as known as olute-carrier 2A9, plays a major role in urate homeostasis by its dual role in urate handling in the kidney and uptake in the liver. For YgfU, it is an E.coli-originated uric acid transporter. Having the same promoter as the two previous projects, in the presence of uric acid, YgfU is expressed, thus, the cell can absorb uric acid.
