The final step in methane formation. Investigations with highly purified methyl-CoM reductase (component C) from Methanobacterium thermoautotrophicum (strain Marburg)

Eur J Biochem. 1988 Mar 15;172(3):669-77. doi: 10.1111/j.1432-1033.1988.tb13941.x.

Abstract

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 mumol 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 microM) and H-S-OcoTP (apparent Ki = 15 microM) were found to be effective inhibitors of methyl-CoM reductase, inhibition being non-competitive with CH3-S-CoM and competitive with H-S-HTP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Disulfides / biosynthesis
  • Euryarchaeota / enzymology
  • Euryarchaeota / metabolism*
  • Methane / biosynthesis*
  • Oxidation-Reduction / drug effects
  • Oxidoreductases / antagonists & inhibitors
  • Oxidoreductases / isolation & purification
  • Oxidoreductases / metabolism*
  • Sulfhydryl Compounds / pharmacology

Substances

  • Disulfides
  • Sulfhydryl Compounds
  • Oxidoreductases
  • methyl coenzyme M reductase
  • Methane