Team:SCUT/Project/Overview

Overview

Cellular compartment is an enclosed space or area that is often used to hold some specific things separated from the cytosol. Different intracellular pH, different enzyme systems and other substances are isolated within the membrane-bound compartments. Due to compartmentalisation and positional assembly a cell can perform different metabolic activities at the same time. This generates a specific micro-environment to regulate or address the multistep processes. Here, we try to enable the development of methodologies that allow a better control over complex synthetic reactions.

Mitochondria is a membrane-enclosed organelle supplying the energy currency of the cell, ATP through respiration. In the tricarboxylic acid (TCA) cycle, each pyruvate molecule produced by glycolysis is actively transported across the inner mitochondrial membrane, and into the matrix where it is oxidized and combined with coenzyme A to form CO2, acetyl-CoA, and NADH. Thus, the environment in the mitochondrial matrix has lower oxygen concentration, higher pH and a more reducing redox potential. This may be beneficial to the enzyme activity needing cofactors in diverse pathways, which are synthesized exclusively in mitochondrial.

To take advantage of the potential attributes of the mitochondrial environment and increase the effective concentration of each component of n-butanol pathway, we transformed the complete n-butanol pathways into the yeast mitochondrial matrix using some leading peptides. Furthermore, the parallel assembly of three carbon sequestration enzymes were organized onto the outer membrane of mitochondria in a designable manner. Thus, the waste byproduct of CO2 released by the TCA cycle was recycled to produce pyruvate, increasing the substrate supply for the n-butanol production (Fig. 1).

    Fig. 1 The engineered pathway. The complete n-butanol pathway was targeted into the mitochondrial matrix. The carbon sequestration enzymes were anchored onto the outer membrane of mitochondria to recycle the CO2 released through TCA. The darkness of the green indicates concentration of CO2: the darkest green marks the highest value.

Compartmentalization of metabolic pathways into a controlled organelle has been proved to increase the target production effectively. Here, a new concept of PAN-compartmentalization is introduced, which not only pays attention to the inner of compartment, but also the outer environment of the target. The core principle of pan-compartmentalization is to achieve the higher enzymes concentration, recycle of byproducts and increase the availability of substrates, so as to achieve as much as possible to maximize carbon recovery and efficient use of coenzymes. Simple word is good understanding and make the best of the environment in/out of the specific compartment.