Sign Up for a Free Account

This is an image preview.
Start a Free Account
to view the full image.

  • Nearly 3,000 illustrations, including video clips of neurologic disorders.

  • Every article is reviewed by our esteemed Editorial Board for accuracy and currency.

  • Full spectrum of neurology in 1,200 comprehensive articles.

  • Listen to MedLink on the go with Audio versions of each article.

Simplified schematic of the reaction of methionine synthase

This reaction serves as the interface of the folate cycle and the methionine remethylation cycle. The coenzyme, cobalamin (vitamin B12), utilizes cobalt to catalyze the transferring function in which the cobalt switches between having 1 or 3 valence electrons, dubbed cob(I)alamin, and cob(III)alamin. Over time, the cob(I)alamin cofactor of methionine synthase becomes oxidized to cob(II)alamin, rendering the enzyme inactive. Regeneration of methionine synthase requires reductive methylation via a reaction catalyzed by methionine synthase reductase in which S-adenosylmethionine is utilized as a methyl donor, reducing cob(II)alamin to cob(I)alamin (not shown). (Illustration created by "Boghog" on September 27, 2019. Modified by Dr. Douglas Lanska. Creative Commons Attribution-Share Alike 4.0 International License.)