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The F 420 H 2 :heterodisulfide oxidoreductase system from Methanosarcina species
Author(s) -
Bäumer Sebastian,
Murakami Eisuke,
Brodersen Jens,
Gottschalk Gerhard,
Ragsdale Stephen W,
Deppenmeier Uwe
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)00555-9
Subject(s) - methanosarcina , oxidoreductase , chemistry , methanogenesis , reductase , electron acceptor , biochemistry , stereochemistry , enzyme , archaea , organic chemistry , methane , gene
F 420 H 2 ‐dependent CoB‐S‐S‐CoM reduction as catalyzed by the F 420 H 2 :heterodisulfide oxidoreductase from Methanosarcina strains was observed in a defined system containing purified F 420 H 2 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 F 420 H 2 were transferred to 2‐hydroxyphenazine by the F 420 H 2 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 F 420 H 2 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 F 420 H 2 ‐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.