|Section2= |Section3= }} Homocysteine's an amino acid with the formula HSCH2CH2CH(NH2)CO2H. It's a homologue of the amino acid cysteine, differing by an additional methylene (-CH2-) group. It's biosynthesized from the methionine by the removal of its terminal Cε methyl group. Homocysteine can be recycled into methionine or converted into cysteine with the aid of B-vitamins. Structure As other amino acids homocysteine exists at neutra pH values as a zwitterion: Biosynthesis and biochemica… (More on Homocysteine)