The F420H2:heterodisulfide oxidoreductase system from Methanosarcina species

FEBS Letters

Ragsdale, Stephen W¹  Bäumer, Sebastian²  Brodersen, Jens²  Deppenmeier, Uwe²  Murakami, Eisuke¹  Gottschalk, Gerhard² 

[1] Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA;Institut für Mikrobiologie und Genetik, Georg-August-Universität, Grisebachstr. 8, 37077 Göttingen, Germany

关键词: Methanogenesis;    Electron transport;    Energy conservation;    Cytochrome;    Quinone;    Phenazine;    CoB-SH;    7-mercaptoheptanoylthreonine phosphate;    CoM-SH;    2-mercaptoethanesulfonate;    F420;    (N-L-lactyl-γ-L-glutamyl)-L-glutamic acid phosphodiester of 7;    8-didemethyl-8-hydroxy-5-deazariboflavin-5′-phosphate;    F420H2;    reduced F420;    Mph;    methanophenazine;    MpH2;    reduced methanophenazine;   

DOI  :  10.1016/S0014-5793(98)00555-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

F₄₂₀H₂-dependent CoB-S-S-CoM reduction as catalyzed by the F₄₂₀H₂:heterodisulfide oxidoreductase from Methanosarcina strains was observed in a defined system containing purified F₄₂₀H₂ dehydrogenase from Methanosarcina mazei Gö1, 2-hydroxyphenazine and purified heterodisulfide reductase from Methanosarcina thermophila. The process could be divided into two partial reactions: (1) reducing equivalents from F₄₂₀H₂ were transferred to 2-hydroxyphenazine by the F₄₂₀H₂ dehydrogenase with a V _max value of 12 U/mg protein; (2) reduced 2-hydroxyphenazine acted as electron donor for CoB-S-S-CoM reduction as catalyzed by the heterodisulfide reductase. The specific activity was 14–16 U/mg protein at 37°C and 60–70 U/mg protein at 60°C. The partial reactions could be combined in the presence of both enzymes. Under these conditions reduced 2-hydroxyphenazine was rapidly oxidized by the heterodisulfide reductase thereby producing the electron acceptor for the F₄₂₀H₂ dehydrogenase. Above a concentration of 50 μM of 2-hydroxyphenazine, the specific activity of the latter enzyme reached the V _max value. When other phenazines or quinone derivatives were used as electron carriers, the activity of F₄₂₀H₂-dependent CoB-S-S-CoM reduction was much lower than the rate obtained with 2-hydroxyphenazine. Thus, this water-soluble analogue of methanophenazine best mimics the natural electron acceptor methanophenazine in aqueous systems.

【 授权许可】

Unknown