Threonine

Threonine is an essential protein-building amino acid whose side chain contains a hydroxyl group. It is encoded by four codons in the standard genetic code.

Amino acid: An organic molecule with amino and carboxyl groups that serves as a protein building block or metabolic intermediate. Threonine is one of the amino acids incorporated into proteins.
Translation (biology): The cellular process that synthesizes a protein by decoding messenger RNA on a ribosome. Ribosomes incorporate threonine when its codons are read.
Dietary reference intake: A set of nutrient intake standards used to assess and plan diets for healthy populations. Threonine requirements are expressed as dietary intake targets.
Serine: A protein-building amino acid with a hydroxyl-bearing side chain and one stereocenter. Serine shares threonine's hydroxyl chemistry but has a shorter side chain.
Essential amino acid: An amino acid that an organism cannot synthesize in sufficient amounts and must obtain through its diet. Humans must obtain threonine from food.
O-linked glycosylation: A post-translational modification that attaches a sugar to the oxygen atom of a protein's serine or threonine residue. Threonine's hydroxyl group provides an attachment site for O-linked sugars.
Protein quality: A measure of how well a dietary protein supplies digestible essential amino acids in appropriate proportions. Threonine can limit the nutritional quality of some protein sources.
Allothreonine: A stereoisomer of threonine that differs in configuration at one of its two stereocenters. Its distinct stereochemistry contrasts with the common protein-incorporated form, L-threonine.
Stereochemistry: The study of the three-dimensional arrangement of atoms in molecules and its effects on chemical properties. Threonine has two stereocenters, giving it four possible stereoisomers.
Protein phosphorylation: The addition of a phosphate group to a protein, often altering its activity or interactions. Protein kinases can phosphorylate threonine's hydroxyl group.

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