Production of CoQ10 in fission yeast by expression of genes responsible for CoQ10 biosynthesis

Identification of novel coenzyme Q10 biosynthetic proteins Coq11 and Coq12 in Schizosaccharomyces pombe

Coenzyme Q (CoQ) is an essential component of the electron transport system in aerobic organisms. CoQ10 has ten isoprene units in its quinone structure and is especially valuable as a food supplement. However, the CoQ biosynthetic pathway has not been fully elucidated, including synthesis of the p-hydroxybenzoic acid (PHB) precursor to form a quinone backbone. To identify the novel components of CoQ10 synthesis, we investigated CoQ10 production in 400 Schizosaccharomyces pombe gene-deleted strains in which individual mitochondrial proteins were lost. We found that deletion of coq11 (an S. cerevisiae COQ11 homolog) and a novel gene designated coq12 lowered CoQ levels to ∼4% of that of the WT strain. Addition of PHB or p-hydroxybenzaldehyde restored the CoQ content and growth and lowered hydrogen sulfide production of the Δcoq12 strain, but these compounds did not affect the Δcoq11 strain. The primary structure of Coq12 has a flavin reductase motif coupled with an NAD+ reductase domain. We determined that purified Coq12 protein from S. pombe displayed NAD+ reductase activity when incubated with ethanol-extracted substrate of S. pombe. Because purified Coq12 from Escherichia coli did not exhibit reductase activity under the same conditions, an extra protein is thought to be necessary for its activity. Analysis of Coq12-interacting proteins by LC-MS/MS revealed interactions with other Coq proteins, suggesting formation of a complex. Thus, our analysis indicates that Coq12 is required for PHB synthesis, and it has diverged among species.

Application of the fission yeast Schizosaccharomyces pombe in human nutrition

Fission yeast Schizosaccharomyces pombe (S. pombe) is renowned as a powerful genetic model for deciphering cellular and molecular biological phenomena, including cell division, chromosomal events, stress responses, and human carcinogenesis. Traditionally, Africans use S. pombe to ferment the beer called 'Pombe', which continues to be consumed in many parts of Africa. Although not as widely utilized as the baker's yeast Saccharomyces cerevisiae, S. pombe has secured several niches in the food industry for human nutrition because of its unique metabolism. This review will explore three specific facets of human nutrition where S. pombe has made a significant impact: namely, in wine fermentation, animal husbandry and neutraceutical supplementation coenzyme Q10 production. Discussions focus on the current gaps in these areas, and the potential research advances useful for addressing future challenges. Overall, gaining a better understanding of S. pombe metabolism will strengthen production in these areas and potentially spearhead novel future applications.

Production of Coenzyme Q10 by microbes: an update

Coenzyme Q₁₀ (CoQ₁₀) is the main CoQ species in human and is used extensively in food, cosmetic and medicine industries because of its antioxidant properties and its benefit in prophylactic medicine and therapy for a variety of diseases. Among various approaches to increase the production of CoQ₁₀, microbial fermentation is the most effective. As knowledge of the biosynthetic enzymes and regulatory mechanisms modulating CoQ₁₀ production increases, opportunities arise for metabolic engineering of CoQ₁₀ in microbial hosts. In this review, we present various strategies used up to date to improve CoQ₁₀ production and focus on metabolic engineering of CoQ₁₀ overproduction in microbes. General strategies of metabolic engineering include providing sufficient precursors for CoQ₁₀, increasing metabolic fluxes, and expanding storage capacity for CoQ₁₀. Based on these strategies, CoQ₁₀ production has been significantly improved in natural CoQ₁₀ producers, as well as in heterologous hosts.

Increasing coenzyme Q10 yield from Rhodopseudomonas palustris by expressing rate-limiting enzymes and blocking carotenoid and hopanoid pathways

Coenzyme Q₁₀ (CoQ₁₀ ), a strong antioxidant, is used extensively in food, cosmetic and medicine industries. A natural producer, Rhodopseudomonas palustris, was engineered to overproduce CoQ₁₀ . For increasing the CoQ₁₀ content, crtB gene was deleted to block the carotenoid pathway. crtB gene deletion led to 33% improvement of CoQ₁₀ content over the wild type strain. However, it was found that the yield of hopanoids was also increased by competing for the precursors from carotenoid pathway with CoQ₁₀ pathway. To further increase the CoQ₁₀ content, hopanoid pathway was blocked by deleting shc gene, resulting in R. palustris [Δshc, ΔcrtB] to produce 4·7 mg g^-1 DCW CoQ₁₀ , which was 1·2 times higher than the CoQ₁₀ content in the wild type strain. The common strategy of co-expression of rate-limiting enzymes (DXS, DPS and UbiA) was combined with the pathway blocking method resulted in 8·2 mg g^-1 DCW of CoQ₁₀ , which was 2·9 times higher than that of wild type strain. The results suggested a synergistic effect among different metabolic engineering strategies. This study demonstrates the potential of R. palustris for CoQ₁₀ production and provides viable strategies to increase CoQ₁₀ titer.

Benzoic acid inhibits Coenzyme Q biosynthesis in Schizosaccharomyces pombe

Coenzyme Q (CoQ, ubiquinone) is an essential component of the electron transport system in aerobic organisms. Human type CoQ₁₀, which has 10 units of isoprene in its quinone structure, is especially valuable as a food supplement. Therefore, studying the biosynthesis of CoQ₁₀ is important not only for increasing metabolic knowledge, but also for improving biotechnological production. Herein, we show that Schizosaccharomyces pombe utilizes p-aminobenzoate (PABA) in addition to p-hydroxybenzoate (PHB) as a precursor for CoQ₁₀ synthesis. We explored compounds that affect the synthesis of CoQ₁₀ and found benzoic acid (Bz) at >5 μg/mL inhibited CoQ biosynthesis without accumulation of apparent CoQ intermediates. This inhibition was counteracted by incubation with a 10-fold lower amount of PABA or PHB. Overexpression of PHB-polyprenyl transferase encoded by ppt1 (coq2) also overcame the inhibition of CoQ biosynthesis by Bz. Inhibition by Bz was efficient in S. pombe and Schizosaccharomyces japonicus, but less so in Saccharomyces cerevisiae, Aureobasidium pullulans, and Escherichia coli. Bz also inhibited a S. pombe ppt1 (coq2) deletion strain expressing human COQ2, and this strain also utilized PABA as a precursor of CoQ₁₀. Thus, Bz is likely to inhibit prenylation reactions involving PHB or PABA catalyzed by Coq2.

CoQ10 production in Schizosaccharomyces pombe is increased by reduction of glucose levels or deletion of pka1

Coenzyme Q (CoQ) is an essential component of the electron transport system that produces ATP in nearly all living cells. CoQ₁₀ is a popular commercial food supplement around the world, and demand for efficient production of this molecule has increased in recent years. In this study, we explored CoQ₁₀ production in the fission yeast Schizosaccharomyces pombe. We found that CoQ₁₀ level was higher in stationary phase than in log phase, and that it increased when the cells were grown in a low concentration of glucose, in maltose, or in glycerol/ethanol medium. Because glucose signaling is mediated by cAMP, we evaluated the involvement of this pathway in CoQ biosynthesis. Loss of Pka1, the catalytic subunit of cAMP-dependent protein kinase, increased production of CoQ₁₀, whereas loss of the regulatory subunit Cgs1 decreased production. Manipulation of other components of the cAMP-signaling pathway affected CoQ₁₀ production in a consistent manner. We also found that glycerol metabolism was controlled by the cAMP/PKA pathway. CoQ₁₀ production by the S. pombe ∆pka1 reached 0.98 mg/g dry cell weight in medium containing a non-fermentable carbon source [2% glycerol (w/v) and 1% ethanol (w/v) supplemented with 0.5% casamino acids (w/v)], twofold higher than the production in wild-type cells under normal growth conditions. These findings demonstrate that carbon source, growth phase, and the cAMP-signaling pathway are important factors in CoQ₁₀ production in S. pombe.

Schizosaccharomyces japonicus has low levels of CoQ10 synthesis, respiration deficiency, and efficient ethanol production

Coenzyme Q (CoQ) is essential for mitochondrial respiration and as a cofactor for sulfide quinone reductase. Schizosaccharomyces pombe produces a human-type CoQ₁₀. Here, we analyzed CoQ in other fission yeast species. S. cryophilus and S. octosporus produce CoQ₉. S. japonicus produces low levels of CoQ₁₀, although all necessary genes for CoQ synthesis have been identified in its genome. We expressed three genes (dps1, dlp1, and ppt1) for CoQ synthesis from S. japonicus in the corresponding S. pombe mutants, and confirmed that they were functional. S. japonicus had very low levels of oxygen consumption and was essentially respiration defective, probably due to mitochondrial dysfunction. S. japonicus grows well on minimal medium during anaerobic culture, indicating that it acquires sufficient energy by fermentation. S. japonicus produces comparable levels of ethanol under both normal and elevated temperature (42 °C) conditions, at which S. pombe is not able to grow.

Cellular factories for coenzyme Q10 production

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.

Programming Saposin-Mediated Compensatory Metabolic Sinks for Enhanced Ubiquinone Production

Microbial synthesis of ubiquinone by fermentation processes has been emerging in recent years. However, as ubiquinone is a primary metabolite that is tightly regulated by the host central metabolism, tweaking the individual pathway components could only result in a marginal improvement on the ubiquinone production. Given that ubiquinone is stored in the lipid bilayer, we hypothesized that introducing additional metabolic sink for storing ubiquinone might improve the CoQ₁₀ production. As human lipid binding/transfer protein saposin B (hSapB) was reported to extract ubiquinone from the lipid bilayer and form the water-soluble complex, hSapB was chosen to build a compensatory metabolic sink for the ubiquinone storage. As a proof-of-concept, hSapB-mediated metabolic sink systems were devised and systematically investigated in the model organism of Escherichia coli. The hSapB-mediated periplasmic sink resulted in more than 200% improvement of CoQ₈ over the wild type strain. Further investigation revealed that hSapB-mediated sink systems could also improve the CoQ₁₀ production in a CoQ₁₀-hyperproducing E. coli strain obtained by a modular pathway rewiring approach. As the design principles and the engineering strategies reported here are generalizable to other microbes, compensatory sink systems will be a method of significant interest to the synthetic biology community.

Cloning and characterization of decaprenyl diphosphate synthase from three different fungi

Coenzyme Q (CoQ) is composed of a benzoquinone moiety and an isoprenoid side chain of varying lengths. The length of the side chain is controlled by polyprenyl diphosphate synthase. In this study, dps1 genes encoding decaprenyl diphosphate synthase were cloned from three fungi: Bulleromyces albus, Saitoella complicata, and Rhodotorula minuta. The predicted Dps1 proteins contained seven conserved domains found in typical polyprenyl diphosphate synthases and were 528, 440, and 537 amino acids in length in B. albus, S. complicata, and R. minuta, respectively. Escherichia coli expressing the fungal dps1 genes produced CoQ₁₀ in addition to endogenous CoQ₈. Two of the three fungal dps1 genes (from S. complicata and R. minuta) were able to replace the function of ispB in an E. coli mutant strain. In vitro enzymatic activities were also detected in recombinant strains. The three dps1 genes were able to complement a Schizosaccharomyces pombe dps1, dlp1 double mutant. Recombinant S. pombe produced mainly CoQ₁₀, indicating that the introduced genes were independently functional and did not require dlp1. The cloning of dps1 genes from various fungi has the potential to enhance production of CoQ₁₀ in other organisms.

Mechanistic Details of Early Steps in Coenzyme Q Biosynthesis Pathway in Yeast

Coenzyme Q (Q) is a redox lipid that is central for the energetic metabolism of eukaryotes. The biosynthesis of Q from the aromatic precursor 4-hydroxybenzoic acid (4-HB) is understood fairly well. However, biosynthetic details of how 4-HB is produced from tyrosine remain elusive. Here, we provide key insights into this long-standing biosynthetic problem by uncovering molecular details of the first and last reactions of the pathway in the yeast Saccharomyces cerevisiae, namely the deamination of tyrosine to 4-hydroxyphenylpyruvate by Aro8 and Aro9, and the oxidation of 4-hydroxybenzaldehyde to 4-HB by Hfd1. Inactivation of the HFD1 gene in yeast resulted in Q deficiency, which was rescued by the human enzyme ALDH3A1. This suggests that a similar pathway operates in animals, including humans, and led us to propose that patients with genetically unassigned Q deficiency should be screened for mutations in aldehyde dehydrogenase genes, especially ALDH3A1.

Biosynthesis of coenzyme Q in eukaryotes

Coenzyme Q (CoQ) is a component of the electron transport chain that participates in aerobic cellular respiration to produce ATP. In addition, CoQ acts as an electron acceptor in several enzymatic reactions involving oxidation-reduction. Biosynthesis of CoQ has been investigated mainly in Escherichia coli and Saccharomyces cerevisiae, and the findings have been extended to various higher organisms, including plants and humans. Analyses in yeast have contributed greatly to current understanding of human diseases related to CoQ biosynthesis. To date, human genetic disorders related to mutations in eight COQ biosynthetic genes have been reported. In addition, the crystal structures of a number of proteins involved in CoQ synthesis have been solved, including those of IspB, UbiA, UbiD, UbiX, UbiI, Alr8543 (Coq4 homolog), Coq5, ADCK3, and COQ9. Over the last decade, knowledge of CoQ biosynthesis has accumulated, and striking advances in related human genetic disorders and the crystal structure of proteins required for CoQ synthesis have been made. This review focuses on the biosynthesis of CoQ in eukaryotes, with some comparisons to the process in prokaryotes.