Rw. Wassenaar et al., PURIFICATION AND CHARACTERIZATION OF DIMETHYLAMINE - 5-HYDROXYBENZIMIDAZOLYL-COBAMIDE METHYLTRANSFERASE FROM METHANOSARCINA-BARKERI FUSARO, European journal of biochemistry, 253(3), 1998, pp. 692-697
Dimethylamine: 5-hydroxybenzimidazolylcobamide methyltransferase (DMA-
MT) was purified from cells of Methanosarcina barkeri Fusaro grown on
trimethylamine. In the presence of methylcobalamine:coenzyme M methylt
ransferase isoenzyme II [MT2(II)] the enzyme quite specifically cataly
zed the stoichiometric conversion of dimethylamine (apparent K-m = 0.4
5 mM) and 7-mercaptoethane-sulfonate (coenzyme M) to monomethylamine a
nd methyl-coenzyme M. Monomethylamine was a competitive inhibitor of t
he reaction (K-i = 4.5 mM). The apparent molecular mass of DMA-MT was
100 kDa and the enzyme was found to be a dimer, composed of identical
50-kDa subunits. A corrinoid content of 0.9 +/- 0.1 mol B-12/mol holoe
nzyme was calculated from HPLC analysis. The as-isolated methyltransfe
rase was inactive, but it could be reductively reactivated. Activation
required the presence of methyltransferase-activating protein. ATP an
d dimethylamine. Incubation with these compounds resulted in the methy
lation of the corrinoid prosthetic group.