The F420H2:heterodisulfide oxidoreductase system from Methanosarcina species. 2-Hydroxyphenazine mediates electron transfer from F420H2 dehydrogenase to heterodisulfide reductase.
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 Vmax 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 degrees C and 60-70 U/mg protein at 60 degrees 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 microM of 2-hydroxyphenazine, the specific activity of the latter enzyme reached the Vmax 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.
Bäumer
S
S
Institut für Mikrobiologie und Genetik, Georg-August-Universität, Göttingen, Germany.
Murakami
E
E
Brodersen
J
J
Gottschalk
G
G
Ragsdale
S W
SW
Deppenmeier
U
U
D000900:Anti-Bacterial Agents / Q000378:metabolism; D004579:Electron Transport; D007700:Kinetics; D017020:Methanosarcina / Q000201:enzymology*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010619:Phenazines / Q000378:metabolism; D013379:Substrate Specificity; D013816:Thermodynamics
D000900:Anti-Bacterial Agents; D010619:Phenazines; C088013:2-hydroxyphenazine; C072742:F420H2 dehydrogenase; D010088:Oxidoreductases; C087171:heterodisulfide reductase