Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedula
Autotrophic Crenarchaeota use two different cycles for carbon dioxide fixation. Members of the Sulfolobales use the 3-hydroxypropionate/4-hydroxybutyrate (HP/HB) cycle, whereas Desulfurococcales and Thermoproteales use the dicarboxylate/4-hydroxybutyrate cycle. While these two cycles differ in the c...
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doaj-7e5fee7af9b54cae9b4b0720409374de2020-11-25T02:20:12ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2020-03-011110.3389/fmicb.2020.00354527437Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedulaLi Liu0Harald Huber1Ivan A. Berg2Institute for Molecular Microbiology and Biotechnology, University of Münster, Münster, GermanyInstitute for Microbiology and Archaeal Center, University of Regensburg, Regensburg, GermanyInstitute for Molecular Microbiology and Biotechnology, University of Münster, Münster, GermanyAutotrophic Crenarchaeota use two different cycles for carbon dioxide fixation. Members of the Sulfolobales use the 3-hydroxypropionate/4-hydroxybutyrate (HP/HB) cycle, whereas Desulfurococcales and Thermoproteales use the dicarboxylate/4-hydroxybutyrate cycle. While these two cycles differ in the carboxylation reactions resulting in the conversion of acetyl-CoA + 2 CO2 to succinyl-CoA, they have a common regeneration part in which succinyl-CoA is reconverted to two acetyl-CoA molecules. This common part includes crotonyl-CoA conversion to acetoacetyl-CoA, which has unequivocally been shown in Ignicoccus hospitalis (Desulfurococcales) and Pyrobaculum neutrophilus (Thermoproteales) to be catalyzed by a bifunctional crotonase/3-hydroxybutyryl-CoA dehydrogenase. It is a fusion protein consisting of an enoyl-CoA hydratase and a dehydrogenase domain. As the homologous bifunctional protein is present in Sulfolobales as well, its common functioning in the conversion of crotonyl-CoA to acetoacetyl-CoA was proposed. Here we show that a model autotrophic member of Sulfolobales, Metallosphaera sedula, possesses in addition to the bifunctional protein (Msed_0399) several separate genes coding for crotonyl-CoA hydratase and (S)-3-hydroxybutyryl-CoA dehydrogenase. Their genes were previously shown to be transcribed under autotrophic and mixotrophic conditions. The dehydrogenase Msed_1423 (and not the bifunctional protein Msed_0399) appears to be the main enzyme catalyzing the (S)-3-hydroxybutyryl-CoA dehydrogenase reaction. Homologs of this dehydrogenase are the only (S)-3-hydroxybutyryl-CoA dehydrogenases present in all autotrophic Sulfolobales, strengthening this conclusion. Two uncharacterized crotonase homologs present in M. sedula genome (Msed_0336 and Msed_0384) were heterologously produced and characterized. Both proteins were highly efficient crotonyl-CoA hydratases and may contribute (or be responsible) for the corresponding reaction in the HP/HB cycle in vivo.https://www.frontiersin.org/article/10.3389/fmicb.2020.00354/full3-hydroxypropionate/4-hydroxybutyrate cycleSulfolobalesMetallosphaera sedulacrotonyl-CoA hydratase3-hydroxybutyryl-CoA dehydrogenase |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Li Liu Harald Huber Ivan A. Berg |
spellingShingle |
Li Liu Harald Huber Ivan A. Berg Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedula Frontiers in Microbiology 3-hydroxypropionate/4-hydroxybutyrate cycle Sulfolobales Metallosphaera sedula crotonyl-CoA hydratase 3-hydroxybutyryl-CoA dehydrogenase |
author_facet |
Li Liu Harald Huber Ivan A. Berg |
author_sort |
Li Liu |
title |
Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedula |
title_short |
Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedula |
title_full |
Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedula |
title_fullStr |
Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedula |
title_full_unstemmed |
Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedula |
title_sort |
enzymes catalyzing crotonyl-coa conversion to acetoacetyl-coa during the autotrophic co2 fixation in metallosphaera sedula |
publisher |
Frontiers Media S.A. |
series |
Frontiers in Microbiology |
issn |
1664-302X |
publishDate |
2020-03-01 |
description |
Autotrophic Crenarchaeota use two different cycles for carbon dioxide fixation. Members of the Sulfolobales use the 3-hydroxypropionate/4-hydroxybutyrate (HP/HB) cycle, whereas Desulfurococcales and Thermoproteales use the dicarboxylate/4-hydroxybutyrate cycle. While these two cycles differ in the carboxylation reactions resulting in the conversion of acetyl-CoA + 2 CO2 to succinyl-CoA, they have a common regeneration part in which succinyl-CoA is reconverted to two acetyl-CoA molecules. This common part includes crotonyl-CoA conversion to acetoacetyl-CoA, which has unequivocally been shown in Ignicoccus hospitalis (Desulfurococcales) and Pyrobaculum neutrophilus (Thermoproteales) to be catalyzed by a bifunctional crotonase/3-hydroxybutyryl-CoA dehydrogenase. It is a fusion protein consisting of an enoyl-CoA hydratase and a dehydrogenase domain. As the homologous bifunctional protein is present in Sulfolobales as well, its common functioning in the conversion of crotonyl-CoA to acetoacetyl-CoA was proposed. Here we show that a model autotrophic member of Sulfolobales, Metallosphaera sedula, possesses in addition to the bifunctional protein (Msed_0399) several separate genes coding for crotonyl-CoA hydratase and (S)-3-hydroxybutyryl-CoA dehydrogenase. Their genes were previously shown to be transcribed under autotrophic and mixotrophic conditions. The dehydrogenase Msed_1423 (and not the bifunctional protein Msed_0399) appears to be the main enzyme catalyzing the (S)-3-hydroxybutyryl-CoA dehydrogenase reaction. Homologs of this dehydrogenase are the only (S)-3-hydroxybutyryl-CoA dehydrogenases present in all autotrophic Sulfolobales, strengthening this conclusion. Two uncharacterized crotonase homologs present in M. sedula genome (Msed_0336 and Msed_0384) were heterologously produced and characterized. Both proteins were highly efficient crotonyl-CoA hydratases and may contribute (or be responsible) for the corresponding reaction in the HP/HB cycle in vivo. |
topic |
3-hydroxypropionate/4-hydroxybutyrate cycle Sulfolobales Metallosphaera sedula crotonyl-CoA hydratase 3-hydroxybutyryl-CoA dehydrogenase |
url |
https://www.frontiersin.org/article/10.3389/fmicb.2020.00354/full |
work_keys_str_mv |
AT liliu enzymescatalyzingcrotonylcoaconversiontoacetoacetylcoaduringtheautotrophicco2fixationinmetallosphaerasedula AT haraldhuber enzymescatalyzingcrotonylcoaconversiontoacetoacetylcoaduringtheautotrophicco2fixationinmetallosphaerasedula AT ivanaberg enzymescatalyzingcrotonylcoaconversiontoacetoacetylcoaduringtheautotrophicco2fixationinmetallosphaerasedula |
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