Which of the following amino acid can carry out one-carbon substitution during the metabolism?

The active form of folic acid (pteroyl glutamate) is tetrahydrofolate. Tetrahydrofolate can carry one-carbon fragments attached to N-5 (formyl, formimino, or methyl groups), N-10 (formyl) or bridging N-5-N-10 (methylene or methenyl groups). The major point of entry for one-carbon fragments into substituted folates is methylene-tetrahydrofolate, which is formed by the reaction of glycine, serine, and choline with tetrahydrofolate. Serine is the most impoant source of substituted folates for biosynthetic reactions, and the activity of serine hydroxymethyltransferase is regulated by the state of folate substitution and the availability of folate. Ref: Bender D.A. (2011). Chapter 44. Micronutrients: Vitamins & Minerals. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.