Abstract
Ubiquinones (UQ) are important electron transporters and play lot of important roles in most organisms. In different species, UQ was classified to be UQ-6, 7, 8, 9, 10 according to their polyprenyl side chain length. The side chain’s length is determined by the enzyme named Poly-Prenyl diphosphate synthases (PPPS). Bacteria are usually reconstructed to producing UQ-10 used in human’s food additive, medicine or cosmetics, such as using decaprenyl Diphosphate Synthase (DPS) gene from R. radiobacter to substitute <em>E.coli’s</em> octaprenyl diphosphate synthase gene , just like <em>E. coli</em> BL21 (△ispB::ddsA) used in this study. It is interesting that not only in these reconstructed bacteria, but in human-being, DPS can synthesize UQ-9 besides UQ-10. The mechanism of this phenomenon is still unknown. In this study, the effects of culture conditions, including the temperature, dissolved oxygen, pH and culture medium, on the DPS characteristics in <em>E. coli</em> BL21 (△ispB::ddsA) were examined. Results show that temperature greatly affects the ratio of UQ-9/UQ-10, but not the total ubiquinone’s production. Increasing dissolved oxygen and protein concentration in culture medium can promote total ubiquinone’s production, but not the ratio of UQ-9/UQ-10. These results may give reference for UQ-10’s industrial produce and the mechanism of these conditions’ effect on DPS will be discussed.
Highlights
Ubiquinones (Coenzyme Q, UQ or CoQ) are essential components for organisms
In our previous study when E. coli BL21 (△ispB::ddsA) was constructed by substituting E. coli octaprenyl diphosphate synthase with decaprenyl Diphosphate Synthase (DPS) from R. radiobacter to produce UQ-10 (Li et al, 2012), we found that E. coli BL21 (△ispB::ddsA) can synthesize UQ-9 besides UQ-10
The E. coli BL21 (△ispB::ddsA) was cultured under different temperatures and the UQ was tested by High Performance Liquid Chromatograph (HPLC)
Summary
Ubiquinones (Coenzyme Q, UQ or CoQ) are essential components for organisms. Their basic function is to transfer electrons in respiratory chain from complex I/II to the cytochrome bc complex in the inner membrane of eukaryote mitochondrion or the plasma membrane of prokaryote (Battino et al, 1990; Brandt and Trumpower, 1994; Lenaz and Genova, 2009). Ubiquinone consists of a redox active benzoquinone ring (4-hydroxybenzoic acid, 4-HB) attached to a polyprenyl side chain. After covalent bond formation between 4-HB and polypreny tail, the resulting 3-polyprenyl-4-hydroxybenzoate (HHB) undergoes several modifications such as hydroxylation, methylation and decarboxylation (Kawamukai, 2002). According to the length of poly-prenyl side chain, ubiquinones could be classified into UQ-6, UQ-7, UQ8, UQ-9 and UQ-10 and different UQ exists in different species.
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