Betaine or folate can equally furnish remethylation to methionine and increase transmethylation in methionine-restricted neonates.

Methionine partitioning between protein turnover and a considerable pool of transmethylation precursors is a critical process in the neonate. Transmethylation yields homocysteine, which is either oxidized to cysteine (i.e.

Dietary methyl donors affect in vivo methionine partitioning between transmethylation and protein synthesis in the neonatal piglet.

Methionine metabolism is critical during development with significant requirements for protein synthesis and transmethylation reactions. However, separate requirements of methionine for protein synthesis and transmethylation are difficult to define because after transmethylation, demethylated methionine is either irreversibly oxidized to cysteine during transsulfuration, or methionine is regenerated by the dietary methyl donors, choline (via betaine) or folate during remethylation. We hypothesized that remethylation contributes significantly to methionine availability and affects partitioning between protein and transmethylation.