Cellular factories for coenzyme Q10 production

Abstract

Coenzyme Q₁₀ (CoQ₁₀), a benzoquinone present in most organisms, plays an important role in the electron-transport chain, and its deficiency is associated with various neuropathies and muscular disorders. CoQ₁₀ is the only lipid-soluble antioxidant found in humans, and for this, it is gaining popularity in the cosmetic and healthcare industries. To meet the growing demand for CoQ₁₀, there has been considerable interest in ways to enhance its production, the most effective of which remains microbial fermentation. Previous attempts to increase CoQ₁₀ production to an industrial scale have thus far conformed to the strategies used in typical metabolic engineering endeavors. However, the emergence of new tools in the expanding field of synthetic biology has provided a suite of possibilities that extend beyond the traditional modes of metabolic engineering. In this review, we cover the various strategies currently undertaken to upscale CoQ₁₀ production, and discuss some of the potential novel areas for future research.

Keywords: Antioxidant; Coenzyme Q10; Industrial biosynthesis; Isoprenoid; Protein engineering; Synthetic biology.

Fig. 1

Chemical structure of coenzyme Q₁₀. This molecule consists of a isoprenoid side chain composed of ten tandemly linked isoprenyl groups attached to a quinone head group

Fig. 2

Biosynthesis of coenzyme Q₁₀. Schematic showing the pathway of various metabolic precursors leading to the formation of the quinone head (PHB), the isoprene tail (decaprenyl diphosphate), and the final Coenzyme Q product. Reflected in red are the various enzymatic steps that are rate limiting. UbiC and UbiA are specific genes from E. coli, and Coq2 is from S. cerevisiae. Unlabelled arrows between chorismate and tyrosine and PHB; FPP and decaprenyl diphosphate; and decaprenyl-4-hydrobenzoic acid and coenzyme Q₁₀ denote the presence of multiple steps that have been abbreviated

Fig. 3

a Protein homology modeling of COQ1 (YBR003W) was performed using ModBase [159] and was viewed using Swiss PDB Viewer [160]. The template for modeling was based on the medium/long-chain length prenyl pyrophosphate synthase of Arabidopsis thaliana (3aq0A) with 42% sequence identity. Helix D and Helix H bind to the elongating isoprene chain and IPP, respectively, at the conserved DDXXD regions. Helix F contains Met-244 and Helix E contains Ser-231, which are thought to be the residues that regulate chain length elongation. The right figure represents the 180° view of that on the left and is superimposed with the structure of CoQ₁₀. b Multiple sequence alignment of Q9X1M1_THEMA (T. maritime TM_1535), ISPB_ECOLI (E. coli IspB), COQ1_SCEREVISIAE (S. cerevisiae COQ1), DPS1_SPOMBE (S. pombe Dps1) and DPS1_HSAPIENS (Human PDSS1) using CLUSTAL W [161]. Helices D (grey), E (green), F (blue), and H (white) indicated in (a), are boxed in (b). Orange underline marks the DDXXD motif. Red asterisks indicate the positions of S. cerevisiae COQ1 Met-244, Ser-247 and Ser-231 residues. Met-244 corresponds to Leu-188 and Leu-231, and Ser-247 to Val-191 and Val-234 of S. pombe Dps1 and H. sapiens PDSS1, respectively. Labels of helices are marked with the same colors as those used for the helices in a

Fig. 4

Spatial metabolic organization with synthetic compartmentalization. Diagrammatic representation of a synthetic proteinaceous or nanotube micro-compartmentalized organelle can be engineered in microbial cells [–151]. The organelle consists of a scaffold on which the biosynthetic enzymes can be immobilized to direct the biochemical flux such that the substrate of an enzyme is the product of another juxtaposed enzyme. Toxic byproducts may conceptually be shunt into sub-compartments within the organelle and sequester therein to ensure optimal growth of the microbial host