Dedicated to Professor Dr Friedhelm Schneider on the occasion of his 60th birthday.
The final step in methane formation
Investigations with highly purified methyl-CoM reductase (component C) from Methanobacterium thermoautotrophicum (strain Marburg)
Article first published online: 3 MAR 2005
European Journal of Biochemistry
Volume 172, Issue 3, pages 669–677, March 1988
How to Cite
ELLERMANN, J., HEDDERICH, R., BÖCHER, R. and THAUER, R. K. (1988), The final step in methane formation. European Journal of Biochemistry, 172: 669–677. doi: 10.1111/j.1432-1033.1988.tb13941.x
- Issue published online: 3 MAR 2005
- Article first published online: 3 MAR 2005
- (Received October 2/December 8, 1987) – EJB 87 1108
Methyl-coenzyme M reductase (= component C) from Methanobacterium thermoautotrophicum (strain Marburg) was highly purified via anaerobic fast protein liquid chromatography on columns of Mono Q and Superose 6. The enzyme was found to catalyze the reduction of methylcoenzyme M (CH3-S-CoM) with N-7-mercaptoheptanoylthreonine phosphate (H-S-HTP = component B) to CH4. The mixed disulfide of H-S-CoM and H-S-HTP (CoM-S-S-HTP) was the other major product formed. The specific activity was up to 75 nmol min−1 mg protein−1. In the presence of dithiothreitol and of reduced corrinoids or titanium(III) citrate the specific rate of CH3-S-CoM reduction to CH4 with H-S-HTP increased to 0.5–2 μmol min−1 mg protein−1. Under these conditions the CoM-S-S-HTP formed from CH3-S-CoM and H-S-HTP was completely reduced to H-S-CoM and H-S-HTP. Methyl-CoM reductase was specific for H-S-HTP as electron donor. Neither N-6-mercaptohexanoylthreonine phosphate (H-S-HxoTP) nor N-8-mercaptooctanoylthreonine phosphate (H-S-OcoTP) nor any other thiol compound could substitute for H-S-HTP. On the contrary, H-S-HxoTP (apparent Ki=0.1 μM) and H-S-OcoTP (apparent Ki= 15 μM) were found to be effectives inhibitors of methyl-CoM reductase, inhibition being non-competitive with CH3-S-CoM and competitive with H-S-HTP.