Part:BBa_K2334002

J23100 + RiboJ + B0034 + pucM, HIU hydrolase generator

The ureide pathway, which produces ureides from uric acid, is an essential purine catabolic process for storing and transporting the nitrogen fixed in leguminous plants and some bacteria. PucM from Bacillus subtilis was recently characterized and found to catalyze the second reaction of the pathway, hydrolyzing 5-hydroxyisourate (HIU), a product of uricase in the first step. PucM has 121 amino acid residues and shows high sequence similarity to the functionally unrelated protein transthyretin (TTR), a thyroid hormone-binding protein. Therefore, PucM belongs to the TTRrelated proteins (TRP) family. In our project, PucM is used as the important enzyme in urate degradation, whose expression is driven by J23100 in this part. RiboJ is used for the quantitive pathway construction.

The metabolic pathway design of the project. The dotted lines represent the enzymes which can accelerate the spontaneous reaction processes. Urate oxidase (uricase, EC 1.7.3.4) is an enzyme with copper bonds that catalyzes the oxidative opening of the purine ring of uric acid to form 5-hydroxyisourate. HIU hydrolase (3.5.2.17) catalyzes the second reaction of the pathway, hydrolyzing 5-hydroxyisourate (HIU), a product of uricase in the first step to form 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU). OHCU is catalyzed by OHCU decarboxylase (4.1.1.97).

Figure 1. pucM was expressed successfully driven by J23100+RiboJ+B0034 gene strucutre. The protein expressed is noted in the figure.

The function of pucM was shown in the urate metabolic pathway. We used the crude bacteria extraction to test the partial or the whole pathway function directly. Before we started to react, the total protein quantity of each sample was made the same. 100ul crude extraction was added into 900ul PBS with urate (PH=8.0). HPLC was performed after reaction for 2h and 100 ℃ heat for 10min.The results show that, pucM did work. The tendency can be explained as follows: when the promoter is too strong, it causes excessive consuming of energy in the bacteria, and the expression of the main enzyme pucL is thus limited; when the promoter is too weak, the reaction can’t attain equilibrium as quickly as with a stronger promoter. So when measured at the time, if the equilibrium was not attained, the performance of the pathway with weaker promoter would be worse. Our modeling result is consistent with our experiment result here. However, the result of separated crude extraction mix experiment can't be explained with the same theory, because when the continuous measurement was performed, performances of different reaction systems with PucL protein were always the same when measured at a time.

Figure 2. The result of crude extraction experiment of BBa_K2334007, BBa_K2334008, BBa_K2334009, BBa_K2334010. The numbers in the figure refer to HPLC original peak area urate decrease. The result shows that the expression ability of pucM does influence the performance of urate consuming. J23106 perform best in the group.

The result of crude extraction experiment of BBa_K2334007, BBa_K2334008, BBa_K2334009, BBa_K2334010. The numbers in the figure refer to HPLC original peak area urate decrease. The result shows that the expression ability of pucM does influence the performance of urate consuming. J23106 perform best in the group.

Figure 3. The result of crude extraction experiment of BBa_K2334012, BBa_K2334013, BBa_K2334014, BBa_K2334015, BBa_K2334016. The numbers in the figure refer to HPLC original peak area urate decrease. The result shows that the expression ability of pucM does influence the performance of urate consuming. J23106 perform best in the group. We compared the effect of pucL together in this group.

Sequence and Features

Assembly Compatibility:

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