279Synthetic Biology: Parts, Devices and Applications, First Edition. Edited by Christina Smolke.
© 2018 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2018 by Wiley-VCH Verlag GmbH & Co. KGaA.
14
14.1 Introduction
Spatial organization is a design principle of life. At the most basic level, compart
mentalization defines the living contents within an organism from the nonliving
extracellular milieu. Inside the cell, the sequestration of processes into distinct
organelles and spaces is a common strategy for enabling competing pathways.
Compartmentalization therefore allows for concurrent metabolic processes that
are thermodynamically out of equilibrium with each other. The chemiosmotic
proton‐motive force is a classic example, in which protons are pumped from the
matrix of the mitochondrion into the intermembrane space, using free energy
derived from electron transfer [1]. By exquisitely regulating this gradient, the cell
can capture its stored energy to synthesize adenosine triphosphate (ATP).
Collapse of the gradient to equilibrium eliminates the mitochondria’s ability to
synthesize ATP and results in cell death.
From a biocatalysis point of view, compartmentalization creates a number of
potential advantages for the engineer. First, it offers an additional way to regulate
pathways [2]. Metabolites can be marked for specific processes in a regulated
fashion, such as in the case of fatty acid oxidation and synthesis, which use
orthogonal pools of fatty acyl‐coenzyme A or fatty acyl–acyl carrier protein
(ACP), respectively. Enzymes can also be selectively regulated via localization,
such as in the glycosome, a peroxisome‐derived organelle found in protozoa [3].
As its name suggests, the glycosome sequesters the first seven enzymes of glyco
lysis into a separate compartment. Its function appears to be regulatory. The
glycosomal enzymes do not possess typical allosteric regulation (e.g., feedback
inhibition of phosphofructokinase), and it is thought that compartmentalization
achieves the same effect [4].
14 Sequestered: Design and Construction of Synthetic Organelles xii Contents
Organelles
Thawatchai Chaijarasphong^1 and David F. Savage2,3
(^1) Mahidol University, Faculty of Science, Department of Biotechnology, Rama VI Rd., Bangkok 10400, Thailand
(^2) University of California, Department of Molecular and Cell Biology, 2151 Berkeley Way, Berkeley, CA 94720, USA
(^3) University of California, Department of Chemistry, 2151 Berkeley Way, Berkeley, CA 94720, USA