Homocysteine, conversion to methionine

There are two major disposal pathways for homocysteine. Conversion to methionine requires folate and vitamin B12-derived cofactors. The formation of cysteine requires vitamin B6(pyridoxine). 

Other compounds involved in one-carbon metabolism are derived from degradation products of choline. Choline, an essential component of certain phospholipids, is oxidized to form betaine aldehyde, which is further oxidized to betaine (trimethylglycine). In the liver, betaine can donate a methyl group to homocysteine to form methionine and dimethyl glycine. This allows the liver to have two routes for homocysteine conversion to methionine. Under conditions in which SAM accumulates, glycine can be methylated to form sarcosine (N-methyl glycine). This route is used when methionine levels are high and excess methionine needs to be metabolized. 

Hexahalobenzenes, mixed, reaction withCuSR 739, 740 reaction with SH and SR 738, 739 Homocysteine, conversion to methionine 618, 619... 

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