Vitamin B12 is an essential vitamin. Its main function is its crucial role as a coenzyme in a step of normal synthesis of myelin. Myelin is required for neuronal protection as well as normal transmission of impulses in the nerves. The one-carbon cycle is vital for the synthesis of myelin and neurotransmitters. Vitamin B12 is crucial for the one-carbon cycle as it acts as a coenzyme for the synthesis of methionine, which, in turn, donates the methyl group required for methylation, in addition, as methionine is formed from homocysteine, if methionine formation is stopped, abnormal amounts of homocysteine accumulate, leading to cognitive disturbances as well as damage to the neurons
Vitamin B12 is an essential coenzyme for the conversion of methylmalonyl-CoA to succinyl CoA, which is a basic requirement for myelin synthesis and stabilization. In the absence of Vitamin B12, methylmalonyl-CoA forms methylmalonic acid (MMA) that forms abnormal fatty acids, leading to abnormal myelination or demyelination. Likewise, it is a vital coenzyme in the synthesis of neurotransmitters. Therefore, vitamin B12 deficiency is linked to a spectrum of neuropsychiatric disorders.
