which is a methyl donor in the synthesis of ..
Synthesis of SAM is dependent on methionine, ..
Methionine synthesis requires at least 4 vitamins. They are B12, folate, vitamin B6 and riboflavin. The intake of these vitamins is thought to be suboptimal in as much as 40% of the population. B12 and folate are the two most likely to be deficient. B12 should be tested by a methylmalonic acid test. Other tests are not as sensitive. Megaloblastic anemia is seen in both folate deficiency as well as B12 deficiency They are the two most common causes of megaloblastic anemia. It is important to know that folic acid (vitamin B9), especially when taken in high doses, can mask the symptoms of a vitamin B12 deficiency. The danger is that without symptoms, someone with a vitamin B12 deficiency may not know it, and could run the risk of developing nerve damage. B12 deficiency can include symptoms such as fatigue, shortness of breath, nervousness, numbness, tingling sensation in the fingers and toes, loss of balance, pale skin, diarrhea, weakness, confusion, memory loss and moodiness. Vitamin B-12 deficiency is often caused by the lack of a protein in the stomach called “intrinsic factor.” Without intrinsic factor, vitamin B-12 can’t be absorbed, regardless of how much you eat.
nism of homeostatic regulation of SAM synthesis in mammalian
3. For the folate independent pathway, (only in the liver and kidney) the enzyme Betaine-homocysteine S-methyltransferase (BHMT) is used to catalyze the remethylation of homocysteine. BHMT is zinc dependent. Glycine betaine or tri methylglycine (TMG) is a methyl group donor derived from choline oxidation. It transfers a methyl group to homocysteine to become methionine. Di-methylglycine (DMG) is a feedback inhibitor here. This pathway appears to be working poorly in people with Chronic Renal Failure where homocysteine is high, DMG is high and zinc is low.
(S−Adenosyl Methionine), which is a methyl donor for ..
There are a variety of substrates needed for proper methylation. The methionine cycle is the heart of the methylation cycle where methylation products are created. This cycle is dependent on other pathways that are connected to it, but the methionine cycle is definitely the place to start. The methionine cycle contains four substrates, methionine (MET), S-Adenosyl Methionine (SAM), S-Adenosyl Homocysteine (SAH), and Homocysteine (HCY). This pathway is all about making S-adenosyl methionine (SAM) which is the Queen of the methylators. For this pathway to function properly a person has to be getting adequate protein. You specifically need the amino acid methionine which will be changed into . The cycle can not even begin before it gets a source of initial methyl groups which comes from . This is the bare bones basic pathway. SAH competes with SAM for for binding to methyltransferase enzymes which acts as competitive inhibition and controls the amount of methylation going on in a cell.