Possible Interaction: S-Adenosylmethionine and Vitamin B 12

“ SAM was significantly correlated with MS activity and vitamin B-12.”

“ Vitamin B12 regulates transmethylation reactions for SAM production and vitamin B6 regulates transsulfuration reactions for GSH production.”

“ Vitamin B12 was a significant determinant of concentrations of AdoMet , tHcy, methylmalonic acid (MMA), and cystathionine.”

“Here we demonstrate that BACE (beta-secretase), as well as PS1, is regulated by methylation and that the reduction of folate and vitamin B12 in culture medium can cause a reduction of SAM levels with consequent increase in presenilin1 and BACE levels and with increase in A beta production.”

“ Vitamin B12 , methylcobalamin, and coenzyme B12 were found to enhance significantly the de novo DNA methylation in the presence of S-adenosylmethionine for concentrations up to 1 microM, but at higher concentrations these compounds were found to inhibit DNA methylation.”

“This outcome is consistent with a double-inversion process, first in the SN2 reaction of cob(I)alamin with SAM to form methylcobalamin and again in a radical transfer of the methyl group from methylcobalamin to the substrate.”

“Analysis of TsrM by … HYSCORE spectroscopies suggests that SAM does not bind to the unique iron site of the cluster in the same manner as in other … (RS) enzymes, yet its binding still perturbs the electronic configuration of both the Fe/S cluster and the cob(II)alamin cofactors.”

“Chemical propylation of the cobalamin prosthetic group inhibited equally and in a light reversible manner methyl group transfer from AMe to H4-folate; from N5-methyl-H4-folate to homocysteine; and from AMe to homocysteine (± H4-folate).”

“From the cofactor activities given by various related compounds in a reduced flavin mononucleotide-dithiothreitol-reducing system, it is tentatively suggested that S-adenosyl-l-methionine activates the vitamin B12 enzyme by methylation.”