The key difference between methyl B12 and B12 is that methyl B12 has an adenosyl ligand in the vitamin B12 structure replaced by a methyl functional group, whereas B12 or vitamin B12 contains an adenosyl functional group attached to the metal center.
The term B12 stands for vitamin B12. However, methyl B12 is a derivative of vitamin B12, which has a methyl group at the place of the adenosyl group of the vitamin B12 molecule.
CONTENTS
1. Overview and Key Difference
2. What is Methyl B12
3. What is B12
4. Methyl B12 vs B12 in Tabular Form
5. Summary – Methyl B12 vs B12
What is Methyl B12?
Methyl B12 or methylcobalamin is a type of cobalamin. Cobalamin is another name for vitamin B12. This compound is different from cyanocobalamin in the way that the cyano group of cobalt is replaced with a methyl group. The methylcobalamin chemical structure has an octahedral cobalt(II) metallic center. This substance appears as bright red-colored crystals. According to coordination chemistry, this substance is a rare compound consisting of metal-alkyl bonds.
Figure 01: The Chemical Structure of Methyl B12
Physiologically, methyl B12 is equivalent to vitamin B12. We can use it to prevent or treat conditions that arise from a lack of vitamin B12 intake – vitamin B12 deficiency. Moreover, this substance is useful in treating peripheral neuropathy, diabetic neuropathy, and amyotrophic lateral sclerosis.
The trade name of methyl B12 is Cobalamin. The major routes of administration for this medication include oral administration, sublingual, and injection. If it is ingested, then it is not used directly as a cofactor. First, it converts into cob(II)alamin by MMACHC. Later, it is converted into two other forms known as adenosylcobalamin and methylcobalamin.
We can produce methylcobalamin in a laboratory through the reduction of cyanocobalamin along with sodium borohydride in the presence of an alkaline solution. This reaction should be followed by the addition of methyl iodide.
Methyl B12 can involve in the Wood-Ljungdahl pathway that is important for some organisms to use carbon dioxide as the source of organic compounds. In this process, the methyl group in the methyl B12 couples with carbon monoxide.
What is B12?
B12 or cobalamin is a water-soluble vitamin that is involved in metabolism. It is important as a cofactor in DNA synthesis and in both fatty acid and amino acid metabolism. Moreover, this substance has a significant role in the normal functioning of the nervous system through its role in the synthesis of myelin. In addition, it has a role in the maturation of red blood cells in the bone marrow.
Vitamin B12 deficiency can occur in developed countries due to impaired absorption that is caused by loss of intrinsic gastric factors. This factor must be bound to a food source consisting of vitamin B12 for the absorption to take place. Another major cause of vitamin B12 deficiency is an age-related decline in stomach acid production. This is because acid exposure can free the protein-bound vitamins.
Figure 02: The Structure of Vitamin B12
When considering the medical uses of vitamin B12 compounds, it is important in repletion of deficiency and in treating cyanide poisoning. We can correct several vitamin B12 deficiencies using frequent intramuscular injections of large doses of the vitamin. This has to be followed by the maintenance of doses of injections or oral dosing at long intervals. During cyanide poisoning, we can use a large amount of hydroxocobalamin intravenously, mostly in combination with sodium thiosulfate. Then the toxic cyanide ion displaces the hydroxycobalamin hydroxide ligand, which results in the formation of nontoxic cyanocobalamin that can be excreted through urine.
What is the Difference Between Methyl B12 and B12?
The term B12 stands for vitamin B12. However, methyl B12 is a derivative of vitamin B12, which has a methyl group at the place of the adenosyl group of the vitamin B12 molecule. The key difference between methyl B12 and B12 is that methyl B12 has the adenosyl ligand in the vitamin B12 structure replaced by a methyl functional group, whereas B12 or vitamin B12 contains an adenosyl functional group attached to the metal center.
The below infographic presents the differences between methyl B12 and B12 in tabular form for side by side comparison.
Summary – Methyl B12 vs B12
Methyl B12 or methylcobalamin is a type of cobalamin. B12 or cobalamin is a water-soluble vitamin that is involved in metabolism. The key difference between methyl B12 and B12 is that methyl B12 has the adenosyl ligand in the vitamin B12 structure replaced by a methyl functional group, whereas B12 or vitamin B12 contains an adenosyl functional group attached to the metal center.
Reference:
1. Smith, Michael W. “Vitamin B12 Deficiency: Causes, Symptoms, and Treatment.” WebMD, WebMD, 3 May 2021.
Image Courtesy:
1. “Methylcobalamin” By Alsosaid1987 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Cyanocobalamin-from-xtal-3D-st-noH” By Ben Mills – Own work (Public Domain) via Commons Wikimedia
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