Activation and reaction kinetics of the dimethylamine/coenzyme M methyltransfer in Methanosarcina barkeri strain Fusaro.
Dimethylamine/5-hydroxybenzimidazolylcobamide methyltransferase (DMA-MT) from Methanosarcina barkeri Fusaro catalyzes (Vmax = 4700 nmol x min(-1) x mg(-1) protein; k(cat) = 7.8 s(-1)) the transfer of a methyl group from dimethylamine (apparent Km = 0.45 mM) to its corrinoid prosthetic group to yield monomethylamine (MMA) and the methylated enzyme. The product, MMA, is a competitive inhibitor of the reaction (apparent Ki = 5.5 mM). The methyl group bound to the corrinoid prosthetic group of DMA-MT is subsequently transferred to coenzyme M in a reaction mediated by methylcobalamin/coenzyme M methyltransferase isoenzyme II [MT2(II)], which binds with high affinity to DMA-MT (apparent Km = 0.22 microM). As isolated, DMA-MT is inactive, but it can enzymically be reactivated by methyltransferase activating protein (MAP), ATP, and hydrogenase. Apart from the established role in corrinoid activation, ATP was found to act as a powerful allosteric effector on the methyltransferase reaction. The results of kinetic studies, supported by the resolution of as-yet partially purified auxiliary protein fractions, demonstrate that DMA-MT, MT2(II), MAP, and hydrogenase are the only enzymic components involved in the dimethylamine/coenzyme M methyltransfer in M. barkeri Fusaro.
Wassenaar
R W
RW
Department of Microbiology, Faculty of Science, University of Nijmegen, The Netherlands. roelw@sci.kun.nl
Keltjens
J T
JT
van der Drift
C
C
D000255:Adenosine Triphosphate / Q000494:pharmacology; D019843:Archaeal Proteins / Q000737:chemistry; D004123:Dimethylamines / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology*; D006864:Hydrogenase / Q000378:metabolism; D007700:Kinetics; D017021:Methanosarcina barkeri / Q000201:enzymology*; D008744:Methylamines / Q000494:pharmacology; D008780:Methyltransferases / Q000737:chemistry*; D011494:Protein Kinases / Q000494:pharmacology
D019843:Archaeal Proteins; D004123:Dimethylamines; D008744:Methylamines; D000255:Adenosine Triphosphate; C034516:dimethylamine; C027451:methylamine; D006864:Hydrogenase; D008780:Methyltransferases; C103170:dimethylamine-coenzyme M methyltransferase; D011494:Protein Kinases; C101667:methyltransferase activation protein, Methanosarcina barkeri