Part:BBa_K4169016:Experience

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Applications of BBa_K4169016

To reduce the amount of trimethylamine (TMA) in the gut,after degradating TMA produced by gut microorganisms, dimethylamine dehydrogenase would catalyse the oxidative demethylation of dimethylamine (DMA) to methylamine and formaldehyde

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The trimethylamine dehydrogenase by 2022 HZAU-iGEM team

Plasmid(4μg) was synthesized by Genscript. Firstly, we centrifuged dmd plasmid powder at 5000rpm for 1 min, then added 40μg sterile ddH2O to dissolve it. The plasmid concentration was 100ng/μL. After diluting plasmid solution into10ng/μL, we transformed plasmids into competent cells E. coli BL21. The outcomes of colony PCR is showed below.

Figure 1. Colony PCR of E. coli BL21containing dmd plasmids.

We performed SDS-PAGE to identify that trimethylamine dehydrogenase can be expressed. Because trimethylamine dehydrogenase (TMADHexist as dimers, the protein molecular weight would double. So, protein molecular weight of TMADH is 164.9kDa.

Figure 1. Control is E. coli BL21 without dmd. dmd is induced E. coli BL21 with dmd.

We cultivated E. coli BL21 containing dmd and E. coli BL21 without dmd (Blank) for about 3 hours (OD600 0.6~0.8). Then they were induced by 4mM theophylline for 9 hours. After adjusting the density of two tubes of bacteria and making them almost have no difference, we added some DMA into bacteria cultures to make the concentration of substrate DMA 5×10-5mol/L and continued to cultivate them. Take samples before we add DMA, and add DMA for 0 min, 10 min, 20min, 3h, 6h, 9h.

This is how we handle bacteria samples. 700 µl bacteria samples were centrifugated at 3000 × g 5 min at 4 °C, take 500µl supernatant. Then 300 µl freshly prepared 10 mM solution of FMOC-Cl in acetonitrile was added, after 1 min, 100 µl 100 mM glycine solution was added to neutralize the reaction.

This is our method of HPLC Supernatant was transferred to new tube for analysis on HPLC system. 10 µl was loaded on to C18 column equilibrated with acetonitrile-buffer (50%) at flow rate 0.75 ml/min. The column was then flushed with a gradient to 100% elutant buffer B (acetonitrile 75% v/v) within 5 min. Ultraviolet absorption of column elutant was monitored (220 nm) and DMA quantification was calculated based on ratio to standard sample peak area.

Results shows that although DMATH can be expressed, we can't confirm it could work in E. coli BL21.

Figure 2. Concentration Changes of Metabolism Substrate DMA

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