Team:Paris/Perspectives

Applying bacterioclock to 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 of 3 enzymes PhaA ,PhaB and PhaC that sequentialy process AcetylcoA into its final product PHA. This biosynthesis is subjected to two 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.