Team:Paris/Perspectives

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Example of an application: Metabolic engineering of polyhydroxyalkanoate biosynthesis pathways

Human overpopulation combined with the current lifestyle urges the rational, efficient, and sustainable use of natural resources to produce environmentally friendly plastic materials. One illustrative example is polyhydroxyalkanoic acids (PHAs), whose production/degradation cycle reduces undesirable wastes and emissions. The biosynthesis of this polymer is currently subject to intensive work. It consists in expressing in appropriate quantities 3 enzymes PhaA ,PhaB and PhaC that sequentialy process AcetoacetylcoA into its final product PHA. This biosynthesis os subjected to 2 contraints :

Intermediate products of this pathway are used in alternatives competing metabolic pathways,
Only the final product is of interest,so that all intermediates products need to be transformed into PHA.

two strategies are commonly used in bioengineering of methabolics pathways :

Sequential expression of enzymes involved in the pathways,
Or constitutive expressions of all enzymes.

Because of the above mentioned limitations, none of these approches are adapted here . Using the sequential expression, intermediate products would accumulate and thus be consummed by competing pathways. Using the constitutive expression a mixture of final and intermediate product would necessarily be obtained.

Our FIFO could be useful here. Indeed a FIFO expression pattern is intermediate between a purely sequential and a purely constitutive expression. At some point all enzymes are presents ( no accumulation of intermediate products ) and during the last step only the last enzyme (PhC) is presents ( all intermediate products are consummed). Moreover, the fact that our system oscillate could provide to the cell a metabolic recovering phase.

More general applications

As for the flagella biosynthesis our FIFO could be useful for many bottom-up assembled molecular machines that needs to be assembled in a precise order. As for the PHA biosynthesis a FIFO could be useful to any pathways subject to competitive alternative pathways and for wich intermediate products must be avoided. We believe that these 2 classes of applications are frequently encountered.

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-== Metabolic engineering of polyhydroxyalkanoate biosynthesis pathways ==
+==  Example of an application: Metabolic engineering of polyhydroxyalkanoate biosynthesis pathways ==
-Human overpopulation combined with the current lifestyle urges the rational, efficient, and sustainable use of natural resources to produce environmentally friendly plastic materials such as polyhydroxyalkanoic acids (PHAs), whose production/degradation cycle reduces undesirable wastes and emissions.
+Human overpopulation combined with the current lifestyle urges the rational, efficient, and sustainable use of natural resources to produce environmentally friendly plastic materials.
-we hope that if we applied our system  to  pathways that have differentes cross linked intermediaries like the biosynthesis of PHA (figure 1), by the FIFO we will optimized the expression of the differentes genes in order to avoid waste producte that will increase impurities.
+One illustrative example is polyhydroxyalkanoic acids (PHAs), whose production/degradation cycle reduces undesirable wastes and emissions.
-Our strategy consists on replacing  the RFP,CFP and YFP genes by the PhaA ,PhaB and PhaC genes in our final system (containing oscillation,FIFO,synchronisation modules).
+The biosynthesis of this polymer is currently subject to intensive work.
+It consists in expressing in appropriate quantities 3 enzymes  PhaA ,PhaB and PhaC that sequentialy process AcetoacetylcoA into its final product PHA.
+This biosynthesis os subjected to 2 contraints :
+* Intermediate products of this pathway are used in alternatives competing metabolic pathways,
+* Only the final product is of interest,so that all intermediates products need to be transformed into PHA.
-This strategy is more efficient than a constitutive activation for 3 main reasons:
+[[Image:PHA.jpg|center]]
-*First, in this application the NADPH, which is a cellular metastable  fuel, is used by  the PhaB to  synthesize bioplastic. This molecule is very important for many metabolic pathways in bacteria. A NADPH recuperation step is then needed to ensure other metabolic activities to go on. We can then make the hypothesis that if the PhaB is always  activated the bacteria will get exhausted and die quickly. In our system, the bacteria will have a NADPH recuperation step, this is why we hope bacteria will live more than in an usual chemoreactor.
-*Secondly, we hope that our system will increase the purity  and the rate of PHA obtain because we don't activate the 3 genes simultaneously, instead of that we activate by a FIFO order  system the 3 genes  so we will avoid lost of acetoacetylcoA or others important intermediary product  in  others metabolic pathways.
+two strategies are commonly used in bioengineering of methabolics pathways :
+* Sequential expression of enzymes involved in the pathways,
+* Or constitutive expressions of all enzymes.
-[[Image:PHA.jpg|center]]
+Because of the above  mentioned limitations, none of these approches are adapted here .
+Using the sequential expression, intermediate products would accumulate and thus be consummed by competing pathways.
+Using the constitutive expression a mixture of final and intermediate product would necessarily be obtained.
-In conclusion,our bacterioclock can be use to obtain many polymers or proteins fibers that their production pass by a lot of methabolic cross linked intermediary, in those situations the FIFO order may optimized the purity and the rate of the final products.
+Our FIFO could be useful here.
+Indeed a FIFO expression pattern is intermediate between a purely sequential and a purely constitutive expression.
+At some point all enzymes are presents ( no accumulation of intermediate products ) and during the last step only the last enzyme (PhC) is presents ( all intermediate products are consummed).
+Moreover, the fact that our system oscillate could provide to the cell a metabolic recovering phase.
-== Bibliography ==
+== More general applications ==
+As for the flagella biosynthesis our FIFO could be useful for many bottom-up assembled molecular machines that needs to be assembled in a precise order.
+As for the PHA biosynthesis a FIFO could be useful to any pathways subject to competitive alternative pathways and for wich intermediate products must be avoided.
+We believe that these 2 classes of applications are frequently encountered.