Is it possible that menaquinone is a more favorable component for electron-transfer processes in prokaryotes under anerobic conditions (and possibly during fatty acid degradation) compared to ubiquinone?
Dear Panagiotis,
The attached chapter entitled "Menaquinone as Well as Ubiquinone as a Crucial Component in the Escherichia coli Respiratory Chain " published in Chemical Biology, Edited by Prof. Deniz Ekinci; ISBN 978-953-51-0049-2; Hard cover, 444 pages; Publisher InTech; Published online 17, February, 2012; Published in print edition February, 2012 describes in details the answer to your question. The following paragraph taken from the chapter might shed light on the answer.
Most Gram-positive bacteria and anaerobic Gram-negative bacteria contain MK as a sole isoprenoid quinone (Collins et al., 1981). Most Bacteroides and Bacillus spp. produce MK as a major isoprenoid quinone. Thermus thermophilus, Actinobacillus actinoides, Thermoplasma acidphilum, Lactobacillus mali, Lactobacillus yamanashiensis, Streptococcus cremoris, Planococcus, Staphylococcus, Corynebacterium, Brevibacterium, Arthrobacter, Chlorobium thiosulfatophium and
Chloropseudomonas ethylicum produce MKs as their sole isoprenoid quinones. Halobacterium and Halococcus have an unsaturated MK (MK-8) and a dihydrogenerated MK (MK-8(H2)) (Kushwaha et al., 1974). Typical strains of species within the genera Actinobacillus and Pasteurella produce DMKs as major isoprenoids. Actinobacillus actinomycetemcomitans, Actinobacillus suis, Pasteurella bettii, Pasteurella pneumotropica, Streptococcus faecalis,
Haemophilus influenza and Haemophilus aergyptilus produce only DMKs. Gram-negative facultatively anaerobic rods and several genera within the family Enterobacteriaceae such as Escherichia, Klebsiella and Promonas contain mixtures of MK and DMK. Certain species of the genera Aeromonas and Erwinia also contain a mixture of MKs. The appearance of MKs on Earth is assumed to be associated with the reducing character of the atmosphere before the occurrence of oxygenic photosynthesis and dramatic increase in environmental oxygen concentration (Schoepp-Cothenet et al., 2009). It is thought that MTK-7
various quinones with higher redox potentials had diverged independently from
naphthoquinones in a few groups of prokaryota along with acquisition of aerobic
metabolism. The reduced form of MKs is highly reactive with molecular oxygen and is subjected to non-catalytic oxidation, and it is therefore thought to function inefficiently in an oxygen-containing atmosphere (Schoepp-Cothenet et al., 2009). The isoprenoid side chain of most MKs consists of 6-10 prenyl units, but MKs bearing 1-5 or 11-14 prenyl units are found in some species (Collins & Jones, 1981). The side chain is generally unsaturated, but it is also partially or fully saturated in some organisms (Collins & Jones, 1981). The degree of
saturation of the side chain appears to be dependent on growth temperature.
Hoping this will be helpful,
Rafik
Dear Panagiotis,
The attached chapter entitled "Menaquinone as Well as Ubiquinone as a Crucial Component in the Escherichia coli Respiratory Chain " published in Chemical Biology, Edited by Prof. Deniz Ekinci; ISBN 978-953-51-0049-2; Hard cover, 444 pages; Publisher InTech; Published online 17, February, 2012; Published in print edition February, 2012 describes in details the answer to your question. The following paragraph taken from the chapter might shed light on the answer.
Most Gram-positive bacteria and anaerobic Gram-negative bacteria contain MK as a sole isoprenoid quinone (Collins et al., 1981). Most Bacteroides and Bacillus spp. produce MK as a major isoprenoid quinone. Thermus thermophilus, Actinobacillus actinoides, Thermoplasma acidphilum, Lactobacillus mali, Lactobacillus yamanashiensis, Streptococcus cremoris, Planococcus, Staphylococcus, Corynebacterium, Brevibacterium, Arthrobacter, Chlorobium thiosulfatophium and
Chloropseudomonas ethylicum produce MKs as their sole isoprenoid quinones. Halobacterium and Halococcus have an unsaturated MK (MK-8) and a dihydrogenerated MK (MK-8(H2)) (Kushwaha et al., 1974). Typical strains of species within the genera Actinobacillus and Pasteurella produce DMKs as major isoprenoids. Actinobacillus actinomycetemcomitans, Actinobacillus suis, Pasteurella bettii, Pasteurella pneumotropica, Streptococcus faecalis,
Haemophilus influenza and Haemophilus aergyptilus produce only DMKs. Gram-negative facultatively anaerobic rods and several genera within the family Enterobacteriaceae such as Escherichia, Klebsiella and Promonas contain mixtures of MK and DMK. Certain species of the genera Aeromonas and Erwinia also contain a mixture of MKs. The appearance of MKs on Earth is assumed to be associated with the reducing character of the atmosphere before the occurrence of oxygenic photosynthesis and dramatic increase in environmental oxygen concentration (Schoepp-Cothenet et al., 2009). It is thought that MTK-7
various quinones with higher redox potentials had diverged independently from
naphthoquinones in a few groups of prokaryota along with acquisition of aerobic
metabolism. The reduced form of MKs is highly reactive with molecular oxygen and is subjected to non-catalytic oxidation, and it is therefore thought to function inefficiently in an oxygen-containing atmosphere (Schoepp-Cothenet et al., 2009). The isoprenoid side chain of most MKs consists of 6-10 prenyl units, but MKs bearing 1-5 or 11-14 prenyl units are found in some species (Collins & Jones, 1981). The side chain is generally unsaturated, but it is also partially or fully saturated in some organisms (Collins & Jones, 1981). The degree of
saturation of the side chain appears to be dependent on growth temperature.
Hoping this will be helpful,
Rafik
Dear Rafik,
Thank you very much for replying and for the attached book chapter!
Regards,
Panagiotis
Dear Prof. Karaman,
Sir, Thank you for providing such a nice answer.
With Best Regards
Pradipta
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