Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus

Pyrococcus furiosus grows optimally near 100°C by fermenting carbohydrates to produce hydrogen (H2) or, if elemental sulfur (S0) is present, hydrogen sulfide instead. It contains two cytoplasmic hydrogenases, SHI and SHII, that use NADP(H) as an electron carrier and a membrane-bound hydrogenase (MBH...

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Main Authors:	Schut, Gerrit J., Nixon, William J., Lipscomb, Gina L., Scott, Robert A., Adams, Michael W. W.
Format:	Online
Language:	English
Published:	Frontiers Research Foundation 2012
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3341082/

id	pubmed-3341082
recordtype	oai_dc
spelling	pubmed-33410822012-05-03 Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus Schut, Gerrit J. Nixon, William J. Lipscomb, Gina L. Scott, Robert A. Adams, Michael W. W. Microbiology Pyrococcus furiosus grows optimally near 100°C by fermenting carbohydrates to produce hydrogen (H2) or, if elemental sulfur (S0) is present, hydrogen sulfide instead. It contains two cytoplasmic hydrogenases, SHI and SHII, that use NADP(H) as an electron carrier and a membrane-bound hydrogenase (MBH) that utilizes the redox protein ferredoxin. We previously constructed deletion strains lacking SHI and/or SHII and showed that they exhibited no obvious phenotype. This study has now been extended to include biochemical analyses and growth studies using the ΔSHI and ΔSHII deletion strains together with strains lacking a functional MBH (ΔmbhL). Hydrogenase activity in cytoplasmic extracts of various strains demonstrate that SHI is responsible for most of the cytoplasmic hydrogenase activity. The ΔmbhL strain showed no growth in the absence of S0, confirming the hypothesis that, in the absence of S0, MBH is the only enzyme that can dispose of reductant (in the form of H2) generated during sugar oxidation. Under conditions of limiting sulfur, a small but significant amount of H2 was produced by the ΔmbhL strain, showing that SHI can produce H2 from NADPH in vivo, although this does not enable growth of ΔmbhL in the absence of S0. We propose that the physiological function of SHI is to recycle H2 and provide a link between external H2 and the intracellular pool of NADPH needed for biosynthesis. This likely has a distinct energetic advantage in the environment, but it is clearly not required for growth of the organism under the usual laboratory conditions. The function of SHII, however, remains unknown. Frontiers Research Foundation 2012-05-01 /pmc/articles/PMC3341082/ /pubmed/22557999 http://dx.doi.org/10.3389/fmicb.2012.00163 Text en Copyright © 2012 Schut, Nixon, Lipscomb, Scott and Adams. http://www.frontiersin.org/licenseagreement This is an open-access article distributed under the terms of the Creative Commons Attribution Non Commercial License, which permits non-commercial use, distribution, and reproduction in other forums, provided the original authors and source are credited.
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Schut, Gerrit J. Nixon, William J. Lipscomb, Gina L. Scott, Robert A. Adams, Michael W. W.
spellingShingle	Schut, Gerrit J. Nixon, William J. Lipscomb, Gina L. Scott, Robert A. Adams, Michael W. W. Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus
author_facet	Schut, Gerrit J. Nixon, William J. Lipscomb, Gina L. Scott, Robert A. Adams, Michael W. W.
author_sort	Schut, Gerrit J.
title	Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus
title_short	Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus
title_full	Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus
title_fullStr	Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus
title_full_unstemmed	Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus
title_sort	mutational analyses of the enzymes involved in the metabolism of hydrogen by the hyperthermophilic archaeon pyrococcus furiosus
description	Pyrococcus furiosus grows optimally near 100°C by fermenting carbohydrates to produce hydrogen (H2) or, if elemental sulfur (S0) is present, hydrogen sulfide instead. It contains two cytoplasmic hydrogenases, SHI and SHII, that use NADP(H) as an electron carrier and a membrane-bound hydrogenase (MBH) that utilizes the redox protein ferredoxin. We previously constructed deletion strains lacking SHI and/or SHII and showed that they exhibited no obvious phenotype. This study has now been extended to include biochemical analyses and growth studies using the ΔSHI and ΔSHII deletion strains together with strains lacking a functional MBH (ΔmbhL). Hydrogenase activity in cytoplasmic extracts of various strains demonstrate that SHI is responsible for most of the cytoplasmic hydrogenase activity. The ΔmbhL strain showed no growth in the absence of S0, confirming the hypothesis that, in the absence of S0, MBH is the only enzyme that can dispose of reductant (in the form of H2) generated during sugar oxidation. Under conditions of limiting sulfur, a small but significant amount of H2 was produced by the ΔmbhL strain, showing that SHI can produce H2 from NADPH in vivo, although this does not enable growth of ΔmbhL in the absence of S0. We propose that the physiological function of SHI is to recycle H2 and provide a link between external H2 and the intracellular pool of NADPH needed for biosynthesis. This likely has a distinct energetic advantage in the environment, but it is clearly not required for growth of the organism under the usual laboratory conditions. The function of SHII, however, remains unknown.
publisher	Frontiers Research Foundation
publishDate	2012
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3341082/
_version_	1611526094355169280

Mutational Analyses of the Enzymes Involved in the Metabolism of Hydrogen by the Hyperthermophilic Archaeon Pyrococcus furiosus

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