The autotrophic 3-hydroxypropionate/4-hydroxybutyrate (HP/HB) cycle functions in thermoacidophilic, (micro)aerobic, hydrogen-oxidizing of the order as well as in mesophilic, aerobic, ammonia-oxidizing Notably, the HP/HB cycle evolved independently in these two archaeal lineages, and crenarchaeal and thaumarchaeal versions differ regarding their enzyme properties and phylogeny. These differences result in altered energetic efficiencies between the variants. Compared to the crenarchaeal HP/HB cycle, the thaumarchaeal variant saves two ATP equivalents per turn, rendering it the most energy-efficient aerobic pathway for carbon fixation. Characteristically, the HP/HB cycle includes two enoyl coenzyme A (CoA) hydratase reactions: the 3-hydroxypropionyl-CoA dehydratase reaction and the crotonyl-CoA hydratase reaction. In this study, we show that both reactions are catalyzed in the aforementioned archaeal groups by a promiscuous 3-hydroxypropionyl-CoA dehydratase/crotonyl-CoA hydratase (Msed_2001 in crenarchaeon and Nmar_1308 in thaumarchaeon ). Although these two enzymes are homologous, they are closely related to bacterial enoyl-CoA hydratases and were retrieved independently from the same enzyme pool by the ancestors of and , despite the existence of multiple alternatives. This striking similarity in the emergence of enzymes involved in inorganic carbon fixation from two independently evolved pathways highlights that convergent evolution of autotrophy could be much more widespread than anticipated. Inorganic carbon fixation is the most important biosynthetic process on Earth and the oldest type of metabolism. The autotrophic HP/HB cycle functions in of the order and in ammonia-oxidizing of the phylum that are highly abundant in marine, terrestrial, and geothermal environments. Bioinformatic prediction of the autotrophic potential of microorganisms or microbial communities requires identification of enzymes involved in autotrophy. However, many microorganisms possess several isoenzymes that may potentially catalyze the reactions of the cycle. Here, we studied the enzymes catalyzing 3-hydroxypropionyl-CoA dehydration and crotonyl-CoA hydration in () as well as in (). We showed that both reactions were catalyzed by homologous promiscuous enzymes, which evolved independently from each other from their bacterial homologs. Furthermore, the HP/HB cycle is of applied value, and knowledge of its enzymes is necessary to transfer them to a heterologous host for synthesis of various value-added products.
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http://dx.doi.org/10.1128/mSphere.01079-20 | DOI Listing |
Sci Total Environ
December 2024
Civil and Environmental Engineering, Technion - Israel Institute of Technology, Haifa 320003, Israel; Environmental Science and Engineering Research Group, Guangdong Technion - Israel Institute of Technology, 241 Daxue Road, Shantou, Guangdong 515063, China; Guangdong Provincial Key Laboratory of Materials and Technologies for Energy Conversion, Guangdong Technion - Israel Institute of Technology, 241 Daxue Road, Shantou, Guangdong 515063, China. Electronic address:
Front Microbiol
July 2021
Institute for Molecular Microbiology and Biotechnology, University of Münster, Münster, Germany.
Ammonia-oxidizing archaea of the phylum Thaumarchaeota are among the most abundant organisms that exert primary control of oceanic and soil nitrification and are responsible for a large part of dark ocean primary production. They assimilate inorganic carbon via an energetically efficient version of the 3-hydroxypropionate/4-hydroxybutyrate cycle. In this cycle, acetyl-CoA is carboxylated to succinyl-CoA, which is then converted to two acetyl-CoA molecules with 4-hydroxybutyrate as the key intermediate.
View Article and Find Full Text PDFmSphere
January 2021
Institute for Molecular Microbiology and Biotechnology, University of Münster, Münster, Germany
The autotrophic 3-hydroxypropionate/4-hydroxybutyrate (HP/HB) cycle functions in thermoacidophilic, (micro)aerobic, hydrogen-oxidizing of the order as well as in mesophilic, aerobic, ammonia-oxidizing Notably, the HP/HB cycle evolved independently in these two archaeal lineages, and crenarchaeal and thaumarchaeal versions differ regarding their enzyme properties and phylogeny. These differences result in altered energetic efficiencies between the variants. Compared to the crenarchaeal HP/HB cycle, the thaumarchaeal variant saves two ATP equivalents per turn, rendering it the most energy-efficient aerobic pathway for carbon fixation.
View Article and Find Full Text PDFFront Microbiol
March 2020
Institute for Molecular Microbiology and Biotechnology, University of Münster, Münster, Germany.
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 CO to succinyl-CoA, they have a common regeneration part in which succinyl-CoA is reconverted to two acetyl-CoA molecules.
View Article and Find Full Text PDFSci Rep
October 2019
Department of Ecology, University of Innsbruck, Innsbruck, Austria.
The Calvin-Benson-Bassham (CBB) cycle and the 3-hydroxypropionate/4-hydroxybutyrate (HP/HB) cycle are two inorganic carbon assimilation pathways widely used by prokaryotic autotrophs in lakes. We investigated the effect of mixing periods and stable water stratification patterns on the trajectories of both CO fixation strategies in a dimictic lake (Piburger See), because information on the spatiotemporal dynamics of prokaryotes using these pathways in freshwater ecosystems is far from complete. Based on a quantitative approach (droplet digital PCR) of genes coding for key enzymes in different CO assimilation pathways, nine depths covering the entire water column were investigated on a monthly basis for one year.
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