O-demethylase from Acetobacterium dehalogenans--substrate specificity and function of the participating proteins

Eur J Biochem. 1998 May 1;253(3):706-11. doi: 10.1046/j.1432-1327.1998.2530706.x.


The ether-cleaving O-demethylase isolated from syringate-grown cells of Acetobacterium dehalogenans (formerly named strain MC) consists of four proteins, components A, B, C and D. The enzyme system converts only phenyl methyl ethers with a hydroxyl group in the ortho position to the methoxyl moiety. The presence of a carboxyl group in the aromatic compound was not required for O-demethylase reaction. Component B mediated the conversion of vanillate to 3,4-dihydroxybenzoate in the presence of the Ti(III)-reduced corrinoid-containing component A. After addition of component D and tetrahydrofolate, methyl tetrahydrofolate was formed from vanillate in stoichiometric amounts. Titanium(III) citrate as a reductant could be replaced by H2, methyl viologen or ferredoxin, partially purified hydrogenase, purified component C obtained from A. dehalogenans, and ATP. From these findings, it was deduced that component B serves as vanillate:corrinoid protein methyltransferase (methyltransferase I) mediating the methyl transfer from vanillate to the reduced corrinoid protein component A. Component D functions as methylcorrinoid protein:tetrahydrofolate transferase (methyltransferase II). The role of component C is probably that of an activating protein reversing accidental oxidation of the protein-bound cob(I)alamin to cob(II)alamin in the presence of ATP and reducing equivalents supplied by the enzymatic oxidation of hydrogen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Gram-Positive Rods / enzymology*
  • Kinetics
  • Methyltransferases / chemistry
  • Methyltransferases / metabolism*
  • Models, Chemical
  • Molecular Sequence Data
  • Oxidation-Reduction
  • Oxidoreductases, O-Demethylating / chemistry*
  • Oxidoreductases, O-Demethylating / metabolism*
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Tetrahydrofolates / metabolism
  • Vanillic Acid / metabolism


  • Tetrahydrofolates
  • 5,6,7,8-tetrahydrofolic acid
  • Oxidoreductases, O-Demethylating
  • Methyltransferases
  • Vanillic Acid