Purification and some properties of the methyl-CoM reductase ofMethanothrix soehngenii

The methyl-CoM reductase from Methanothrix soehngenii was purified 18-fold to apparent homogeneity with 50% recovery in three steps. The native molecular mass of the enzyme estimated by gel-fitration was 280 kDa. SDS-polyacrylamide gel electrophoresis revealed three protein bands corresponding to Mr 63 900, 41 700 and 30 400 Da. The methyl-coenzyme M reductase constitutes up to 10% of the soluble cell protein. The enzyme has Km apparent values of 23 μM and 2 mM for N-7-mercaptoheptanoylthreonine phosphate (HS- HTP=componentB) and methyl-coenzyme M (CH3?CoM) respectively. At the optimum pH of 7.0 60 nmol of methane were formed per min per mg protein.