Liu, Li and Hubert, Harald and Berg, Ivan A. (2020) Enzymes Catalyzing Crotonyl-CoA Conversion to Acetoacetyl-CoA During the Autotrophic CO2 Fixation in Metallosphaera sedula. FRONTIERS IN MICROBIOLOGY, 11: 354. ISSN 1664-302X,
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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.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CARBON-DIOXIDE ASSIMILATION; 4-HYDROXYBUTYRYL-COA DEHYDRATASE; 3-HYDROXYPROPIONATE CYCLE; ACETYL-COENZYME; HYDROGEN; PATHWAY; CARBOXYLASE; SYNTHETASE; EVOLUTION; REDUCTASE; 3-hydroxypropionate; 4-hydroxybutyrate cycle; Sulfolobales; Metallosphaera sedula; crotonyl-CoA hydratase; 3-hydroxybutyryl-CoA dehydrogenase |
| Subjects: | 500 Science > 570 Life sciences |
| Divisions: | Biology, Preclinical Medicine > Institut für Biochemie, Genetik und Mikrobiologie > Lehrstuhl für Mikrobiologie (Archaeenzentrum) |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 29 Mar 2021 08:32 |
| Last Modified: | 29 Mar 2021 08:32 |
| URI: | https://pred.uni-regensburg.de/id/eprint/44947 |
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