Metabohsm methyl groups

Folic acid and vitamin B]2 metabohsm are linked by the reaction that transfers a methyl group from 5-MTHF to cobalamin. In cases of cobalamin deficiency, folate is trapped as 5-MTHF and is metabolically dead. It cannot... 

Several metabolic pathways (e.g. hpid metabohsm, creatine and carnitine synthesis) require methyl groups and these can be snppUed by choline or methionine. During the process of transmethylation, betaine, a tertiary amine, is formed by the oxidation of choline. Betaine can be added to the diet to act as a more direct supply of methyl groups, thus sparing choUne for its other fimctions of lecithin and acetylcholine formation, and methionine for protein synthesis. Betaine occurs in sugar beet. 

Capsaicin and capsaicinoids undergo Phase I metabolic bioconversion to catechol metabolites via hydroxylation of the vanillyl ring moiety (Lee and Kumar, 1980 Miller et al, 1983). Metabohsm involves oxidative, in addition to non-oxidative, mechanisms. An example of oxidative conversion involves the liver mixed-function oxidase system to convert capsaicin to an electrophilic epoxide, a reactive metabolite (Olajos, 2004). Surh and Lee (1995) have also demonstrated the formation of a phenoxy radical and quinine product the quinine pathway leads to formation of a highly reactive methyl radical (Reilly et al, 2003). The alkyl side chain of capsaicin also undergoes rapid oxidative deamination (Wehmeyer et al, 1990) or hydroxylation (Surh et al, 1995 Reilly et al, 2003) to hydroxycapsaicin as a detoxification pathway. An example of nonoxidative metabolism of capsaicin is hydrolysis of the acid-amide bond to yield vanillylamide and fatty acyl groups (Kawada et al, 1984 Oi et al, 1992). 

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