Recycling of HomocysteineHomocysteine is a toxic amino acid, which is normally well controlled through the liver with the help ofB vitamains which convert it to non-toxic amino acids, among them Methionine. But when these pathsare blocked, or unavailable, homocysteine builds up in body tissues. When given to test animals, itinduces the initial stages of arteriosclerosis.When our body recycles homocysteine and turns into methionine, a so called methyl donor is needed.Methyltetrahydrofolate is the methyl donor. This is the reaction:
MTHF is turned into THD when it gives away the methyl group. This methyl group goes to tetra hydro-bio- pterin or 4 BH.
4BH gets turned into q-pterinand this helps convert aromatic amino acids to ring-hydroxylatedderivatives e.g., phenylalanine (Phe) tyrosine (Tyr) using a tetrahydropterin as electron donor.Remember norepinephrine and dopamine formation need this reaction.