mə̇ˈthīəˌnēn, -_nə̇n noun
Etymology: International Scientific Vocabulary me- (from methyl ) blend of meth- + thion- + -ine
: a crystalline essential amino acid CH 3 SCH 2 CH 2 CH(NH 2 )COOH that occurs in the l -form as a constituent of many proteins (as casein and egg albumin), that is important especially as a source of sulfur for the biosynthesis of cystine and as a source of methyl groups for transmethylation reactions (as in the biosynthesis of choline, creatine, and adrenaline), that is prepared synthetically in the racemic dl -form, and that is used as a dietary supplement for humans and their domestic mammals and poultry and in the treatment of fatty infiltration of the liver; α-amino-γ-methyl-mercapto-butyric acid