Hi to Rich, can you please explain something about methionine-synthase, it is: As I know methionine-synthase (MTR) transfers the methyl group from methyl-folate to B12 so that methyl-b12 is generated then methionine-synthase transfers the methyl-group from methyl-b12 to homocystein and remethylates to methionine. During this process the B12 as a cofactor of methionine-sysnthase becaomes oxidized and must be regenerated. This is the job of the methionine-synthase-reductase (MTRR). Yasko wirites that for regenartion of B12 SAMe is needed but I dont understand this because the methyl group to methylate B12 comes form methyl-folate and not from SAMe or is it if there is not enough methyl-folate then the methyl-group comes form SAMe?? It wouldnt make sense to first use up SAMe and then generate SAMe again. And does methyl-B12 becomes OH-b12 after the transfer of the methyl group to homocystein? So what I need to kno is the exact mechanism of MTR/MTRR I couldnt find this in detail anywhere. CAn you explain it please? And then Ive got another question, do the different B12s compete with each other for transport into the cell? Could this be a reason why methyl-b12 is tolaerated and oh-b12 and others not because they would suppress the use of methyl-b12 if anyway methyl-b12 is very low or on the other hynd if OH-B12 uses up SAMe this could also be a reason why OH-B12 might be tolerated bad and methyl-B12 is tolerated good. Thanks to you Rich.