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Ubiquinone Biosynthesis from Thermo Fisher Scientific, …

AB - Transcription of the cobinamide biosynthetic genes (the CobI operon) was induced under three different physiological conditions: anaerobiosis (anaerobic respiration or fermentation), aerobic respiration at low oxygen levels, and aerobic respiration with a partial block of the electron transport chain. After a shift to inducing conditions, there was a time lag of approximately 50 min before the onset of CobI induction. Under conditions of anaerobic respiration, the level of CobI transcription was dependent on the nature of both the electron donor (carbon and energy source) and the acceptor. Cells grown with electron acceptors with a lower midpoint potential showed higher CobI expression levels. The highest level of CobI transcription observed was obtained with glycerol as the carbon source and fumarate as the electron acceptor. The high induction seen with glycerol was reduced by mutational blocks in the glycerol catabolic pathway, suggesting that glycerol does not serve as a gratuitous inducer but must be metabolized to stimulate CobI transcription. In the presence of oxygen, CobI operon expression was induced 6- to 20-fold by the following: inhibition of cytochrome o oxidase with cyanide, mutational blockage of ubiquinone biosynthetis, and starvation of mutant cells for heme. We suggest that the CobI operon is induced in response to a reducing environment within the cell and not by the absence of oxygen per se.

T1 - Biosynthesis of ubiquinone compounds with conjugated prenyl side chains

Ubiquinone (also known as coenzyme Q) is a ubiquitous lipid-soluble redox cofactor that is an essential component of electron transfer chains. Eleven genes have been implicated in bacterial ubiquinone biosynthesis, including ubiX and ubiD, which are responsible for decarboxylation of the 3-octaprenyl-4-hydroxybenzoate precursor. Despite structural and biochemical characterization of UbiX as a flavin mononucleotide (FMN)-binding protein, no decarboxylase activity has been detected. Here we report that UbiX produces a novel flavin-derived cofactor required for the decarboxylase activity of UbiD. UbiX acts as a flavin prenyltransferase, linking a dimethylallyl moiety to the flavin N5 and C6 atoms. This adds a fourth non-aromatic ring to the flavin isoalloxazine group. In contrast to other prenyltransferases, UbiX is metal-independent and requires dimethylallyl-monophosphate as substrate. Kinetic crystallography reveals that the prenyltransferase mechanism of UbiX resembles that of the terpene synthases. The active site environment is dominated by π systems, which assist phosphate-C1' bond breakage following FMN reduction, leading to formation of the N5-C1' bond. UbiX then acts as a chaperone for adduct reorientation, via transient carbocation species, leading ultimately to formation of the dimethylallyl C3'-C6 bond. Our findings establish the mechanism for formation of a new flavin-derived cofactor, extending both flavin and terpenoid biochemical repertoires.

Ubiquinol biosynthesis (Homo sapiens) - WikiPathways

Keyword - Ubiquinone biosynthesis (KW-0831)

Transcription of the cobinamide biosynthetic genes (the CobI operon) was induced under three different physiological conditions: anaerobiosis (anaerobic respiration or fermentation), aerobic respiration at low oxygen levels, and aerobic respiration with a partial block of the electron transport chain. After a shift to inducing conditions, there was a time lag of approximately 50 min before the onset of CobI induction. Under conditions of anaerobic respiration, the level of CobI transcription was dependent on the nature of both the electron donor (carbon and energy source) and the acceptor. Cells grown with electron acceptors with a lower midpoint potential showed higher CobI expression levels. The highest level of CobI transcription observed was obtained with glycerol as the carbon source and fumarate as the electron acceptor. The high induction seen with glycerol was reduced by mutational blocks in the glycerol catabolic pathway, suggesting that glycerol does not serve as a gratuitous inducer but must be metabolized to stimulate CobI transcription. In the presence of oxygen, CobI operon expression was induced 6- to 20-fold by the following: inhibition of cytochrome o oxidase with cyanide, mutational blockage of ubiquinone biosynthetis, and starvation of mutant cells for heme. We suggest that the CobI operon is induced in response to a reducing environment within the cell and not by the absence of oxygen per se.


Examination of the aromatic aminoacid biosynthesis pathway in Chlamydia trachomatis revealed that the chorismate biosynthesis portion of the pathway was intact, however most enzymes necessary for the conversion of chorsimate to the 3 branch aromatic aminoacids were not present (only tyrB, trpA/B and trpF have been identified in Chlamydia trachomatis). This truncated aromatic amino acid biosynthesis pathways in Chlamydia trachomatis give rise to end product -chorismate that are used as intermediates for other biosynthetic pathways. So the ubiquinone, folate, menaquinone and enterobactin biosynthesis pathway have been searched in Chlamydia trachomatis. About half of the ubiquinone and folate biosynthesis pathways genes appear in Chlamydia trachomatis, however almost all of genes for menaquinone and enterobactin biosynthesis are missing. In folic acid biosyntheses pathway, Chlamydia trachomatis is missing pabA, pabB (encoding aminodeoxychorismate synthase) and pabC (encoding aminodeoxychorismate lyase), which catalyze the reaction from chorismate to p-aminobenzoate. We suppose this means that Chlamydia trachomatis might depend on the host to supply PABA for folic acid biosynthesis. In ubiquinone biosynthesis pathway, Chlamydiae trachomatis contain homologs of ubiA (encoding 4-hydroxybenzoate octaprenyltransferase); ubiX (encoding 3-octaprenyl-4-hydroxybenzoate decarboxylase) and ubiE (2-octaprenyl-6-methoxy-1, 4-benzoquinone methylase), the genes encoding the rest 5 steps of reactions are missing.

It is very interesting that the chorismate biosynthetic pathway genes in CT are in the same operon except the first gene aroA is at difference place. In many microbial eukaryotes, the aroM gene from fungi encodes a single polypeptide that catalyses five consecutive steps of the chorismate biosynthetic pathway. If the genes encoding enzymes in the common-pathway portion of aromatic biosynthesis are named in order of reaction sequence (i.e., aroA-aroG), the domain order in aroM gene is aroB*aroF*aroE*aroC*aroD.

Ubiquinone biosynthesis in microorganisms - …

regulator and demonstrated that it controls folate and ubiquinone biosynthesis.

Seven ubiquinone-deficient mutants of Escherichia coli, each of which accumulates two phenolic precursors of ubiquinone, have been characterized, and the accumulated compounds have been identified. The mutants accumulate small quantities of 2-octaprenyl-6-methoxyphenol, which was isolated and characterized by nuclear magnetic resonance and mass spectrometry, and relatively large amounts of 2-octaprenylphenol, a compound previously identified from E. coli. They also accumulate small quantities of a compound identified as 2-(hydroxyoctaprenyl)phenol although the relevance of this compound to the biosynthesis of ubiquinone is not clear. The results of genetic analysis suggest that each of the mutants carries a mutation in a gene (designated ubiH) which is located at about min 56 on the E. coli chromosome and is co-transducible with the serA and lysB genes. Based on information obtained from this and previous studies with ubiquinone-deficient mutants, a pathway is proposed for ubiquinone biosynthesis in E. coli, and a summary of the known gene-enzyme relationships is given.

N2 - Transcription of the cobinamide biosynthetic genes (the CobI operon) was induced under three different physiological conditions: anaerobiosis (anaerobic respiration or fermentation), aerobic respiration at low oxygen levels, and aerobic respiration with a partial block of the electron transport chain. After a shift to inducing conditions, there was a time lag of approximately 50 min before the onset of CobI induction. Under conditions of anaerobic respiration, the level of CobI transcription was dependent on the nature of both the electron donor (carbon and energy source) and the acceptor. Cells grown with electron acceptors with a lower midpoint potential showed higher CobI expression levels. The highest level of CobI transcription observed was obtained with glycerol as the carbon source and fumarate as the electron acceptor. The high induction seen with glycerol was reduced by mutational blocks in the glycerol catabolic pathway, suggesting that glycerol does not serve as a gratuitous inducer but must be metabolized to stimulate CobI transcription. In the presence of oxygen, CobI operon expression was induced 6- to 20-fold by the following: inhibition of cytochrome o oxidase with cyanide, mutational blockage of ubiquinone biosynthetis, and starvation of mutant cells for heme. We suggest that the CobI operon is induced in response to a reducing environment within the cell and not by the absence of oxygen per se.

MetaCyc ubiquinol-10 biosynthesis (eukaryotic)
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Structural Insights into Ubiquinone Biosynthesis in Membranes

The results demonstrate that peroxisomes are involved in ubiquinone biosynthesis, and at least two enzymes of the biosynthetic sequence are present in this organelle.

Biosynthesis of ubiquinones requires the ..

AB - Enzymatic steps from two different biosynthetic pathways were combined in Escherichia coli, directing the synthesis of a new class of biomolecules - ubiquinones with prenyl side chains containing conjugated double bonds. This was achieved by the activity of a C30 carotenoid desaturase, CrtN, from Staphylococcus aureus, which exhibited an inherent flexibility in substrate recognition compared to other carotenoid desaturases. By utilizing the known plasticity of E. coli's native ubiquinone biosynthesis pathway and the unusual activity of CrtN, modified ubiquinone structures with prenyl side chains containing conjugated double bonds were generated. The side chains of the new structures were confirmed to have different degrees of desaturation by mass spectrometry and nuclear magnetic resonance analysis. In vivo 14C labeling and in vitro activity studies showed that CrtN desaturates octaprenyl diphosphates but not the ubiquinone compounds directly. Antioxidant properties of conjugated side chain ubiquinones were analyzed in an in vitro β-carotene-linoleate model system and were found to be higher than the corresponding unmodified ubiquinones. These results demonstrate that by combining pathway steps from different branches of biosynthetic networks, classes of compounds not observed in nature can be synthesized and structural motifs that are functionally important can be combined or enhanced.

K06126 ubiquinone biosynthesis monooxygenase Coq6 [EC:1.14.13.-] ..

The results demonstrate that peroxisomes are involved in ubiquinone biosynthesis, and at least two enzymes of the biosynthetic sequence are present in this organelle.">

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