Pathways of energy conservation in methanogenic archaea |
| |
Authors: | U Deppenmeier V Müller G Gottschalk |
| |
Institution: | (1) Institut für Mikrobiologie, Georg-August-Universität Göttingen, Grisebachstrasse 8, D-37077 Göttingen, Germany |
| |
Abstract: | Methanogenic archaea are strictly anaerobic organisms that derive their metabolic energy from the conversion of a restricted number of substrates to methane. H2+CO2 and formate are converted to CH4 via the CO2-reducing pathway, while methanol and methylamines are metabolized by the methylotrophic pathway. A limited number of methanogenic organisms utilize acetate by the aceticlastic pathway. Redox reactions involved in these processes are partly catalyzed by membrane-bound enzyme systems that generate or, in the case of endergonic reactions, use electrochemical ion gradients. The H2:heterodisulfide oxidoreductase, the F420H2:heterodisulfide oxidoreductase and the CO:heterodisulfide oxidoreductase, are novel systems that generate a proton motive force by redox-potential-driven H+ translocation. The methyltetrahydromethanopterin:coenzyme M methyltransferase is a unique, reversible sodium ion pump that couples methyl transfer with the transport of Na+ across the cytoplasmic membrane. Formylmethanofuran dehydrogenase is a reversible ion pump that catalyzes formylation and deformylation, of methanofuran. In summary, the pathways are coupled to the generation of an electrochemical sodium ion gradient and an electrochemical proton gradient. Both ion gradients are used directly for ATP synthesis via membrane integral ATP synthases. The function of the above-mentioned systems and their components in the metabolism of methanogens are described in detail.Abbreviations
DCCD N,N
dicyclohexylcarbodiimide
-
F
420
(N-l-Lactyl--l-glutamyl)-l-glutamic acid phosphodiester of 7,8 didemethyl-8-hydroxy-5-deazariboflavin-5-phosphate
-
H
4MPT
Tetrahydromethanopterin
-
HS-CoM
2-Mercaptoethanesulfonate
-
HS-HTP
7-Mercaptoheptanoyl-O-phospho-l-threonine
-
MF
Methanofuran
-
Ms
Methanosarcina
-
Mc
Methanococcus
-
Mb
Methanobacterium
-
SF 6847
3,5-Di-tert-butyl-4-hydroxybenzylidene-malononitrile
-
Electrochemical sodium ion gradient
-
Electrochemical proton gradient |
| |
Keywords: | Methanosarcina Methanobacterium Hydrogenase Heterodisulfide reductase CO dehydrogenase Methyltransferase Formylmethanofuran dehydrogenase ATP synthase Proton motive force Sodium motive force |
本文献已被 SpringerLink 等数据库收录! |
|