INCI Line: INCI: Threonine - Also known as: L-Threonine, Thr, T

QUICK FACTS

What is Threonine?

Threonine is an essential amino acid, meaning the human body cannot synthesize it independently and it must be obtained from external sources. It is one of only two amino acids in the standard group that carries a hydroxyl group directly on its side chain (the other being serine), giving it a hydrophilic character that makes it one of the more water-attracting members of the amino acid family. This polarity is directly relevant to its contribution to the skin's natural moisturizing factor (NMF) - the collection of hygroscopic compounds within the stratum corneum associated with water retention and skin suppleness.

In proteins, threonine's hydroxyl group makes it a frequent target for glycosylation and phosphorylation - two of the most common post-translational modifications that regulate protein activity. In the skin's structural proteins, including components of the extracellular matrix, threonine residues participate in the cross-linking and modification events that contribute to protein stability. This positions threonine as both an NMF-level humectant amino acid and a structurally relevant component of the broader skin protein environment.

At Sweet Chemistry, threonine occupies the final position in the eleven-amino-acid complex across the three water-based formulas - completing the most comprehensive topical amino acid blend in the product's category and reflecting the brand's approach of using a full spectrum of skin-identical components rather than selecting for one or two headline names.

What does it do for skin?

In topical application, threonine contributes to the NMF water-binding network through its hydrophilic side chain. Like serine, its hydroxyl group associates readily with water molecules, supporting the moisture-retaining environment of the uppermost stratum corneum layers alongside PCA, sodium PCA, sodium lactate, and the other amino acids in the blend.

Threonine is also studied in connection with the glycine-serine metabolic pathway - as a metabolic precursor to glycine in certain cellular contexts, threonine's presence in a formula alongside glycine adds a degree of metabolic relevance to the two amino acids' co-occurrence. Glycine is the single most abundant amino acid in collagen, and the pathway connecting threonine to glycine biosynthesis gives threonine an indirect research-based association with the same collagen environment that Matrikynes® peptides address more directly.

As the last amino acid listed in Sweet Chemistry's eleven-amino-acid complex, threonine completes a blend designed to replicate the actual free amino acid profile of healthy skin's NMF as completely as possible. No individual amino acid in the blend is redundant - each contributes a distinct chemical character, charge, and side-chain functionality that contributes to the overall hydration environment in a way that isolating any single amino acid would not achieve.

Found In

In 3 Formulas as Part of the 1% Amino Acid Blend

Threonine completes Sweet Chemistry's eleven-amino-acid NMF complex, present across all three water-based formulas as the final member of a full-spectrum amino acid approach to surface hydration.

Nourishment - All Skin Types

Barrier Repairing Hydra-Serum 1% Amino Acid Blend (incl. Threonine) - 1.0 oz / 30 ml

The Hydra-Serum pairs the full eleven-amino-acid complex with PCA, sodium PCA, sodium lactate, and four forms of hyaluronic acid in a 40%-active water-based emulsion designed for all skin types.

Hydration - Dry to Normal

Elasticity Reinforcing Hydra-Cream 1% Amino Acid Blend (incl. Threonine) - 1.7 oz / 50 ml

The Hydra-Cream delivers the full amino acid complex alongside 3% Matrikynes® peptides and 2% THD ascorbate in a cushioned satin finish for dry to normal skin.

Hydration - Dry to Dehydrated

Elasticity Reinforcing Lipid-Cream 1% Amino Acid Blend (incl. Threonine) - 1.7 oz / 50 ml

In the Lipid-Cream, the full amino acid complex contributes NMF hydration support within the most emollient formula in the lineup, alongside shea butter and a complete ceramide barrier blend.

Works Together With

Collagen Amino Acid Glycine

INCI: Glycine.

The most abundant amino acid in collagen, present alongside threonine in all three water-based formulas. Synergy Note: Threonine is studied as a metabolic precursor to glycine in certain cellular pathways - their co-formulation addresses both the finished collagen amino acid and a potential source of additional glycine within the same topical blend.

NMF Amino Acid Serine

INCI: Serine.

The other hydroxyl-bearing amino acid in the blend, present alongside threonine in all three water-based formulas. Synergy Note: Threonine and serine are the only two amino acids in the standard set with a hydroxyl group on the side chain - their co-presence creates a dual-hydroxyl amino acid contribution to the NMF water-binding network.

NMF Component PCA (Pyrrolidone Carboxylic Acid)

INCI: PCA.

A skin-identical NMF component present in all three water-based formulas alongside the amino acid blend. Synergy Note: PCA is the dominant NMF humectant fraction; threonine and the other amino acids together form the largest NMF fraction by count - their combined presence recreates the full biochemical composition of healthy skin's moisture management system.

ECM Peptide Complex Matrikynes® Bone Peptides

INCI: Hydrolyzed Cow Bone Extract.

At 3% in all four formulas, associated with improvements in the appearance of skin density and aging signs. Synergy Note: Threonine contributes to the local amino acid pool in the epidermis - the substrate environment in which Matrikynes® peptide-related renewal activity takes place.