Polyglutamic Acid
Also known as: γ-PGA, Gamma-Polyglutamic Acid
Description
Polyglutamic acid (γ-PGA) is a high molecular weight biopolymer composed of repeating glutamic acid units linked through γ-amide bonds, naturally produced by fermentation of Bacillus subtilis (notably in the Japanese food natto). With a molecular weight ranging from 50 kDa to over 2,000 kDa, γ-PGA is reported to hold up to 5,000 times its weight in water — approximately five times the water-binding capacity of hyaluronic acid. Its large molecular size means it primarily acts on the skin surface, forming a hydrating film that reduces transepidermal water loss. Notably, γ-PGA also inhibits hyaluronidase, the enzyme responsible for hyaluronic acid degradation, thereby preserving endogenous HA levels in the dermis and epidermis. This dual action — direct hydration and HA preservation — makes it a potent moisturizing active for aging and dehydrated skin.
Mechanism of Action
γ-PGA functions through multiple hydration-enhancing mechanisms. Its polyanionic carboxylate groups form extensive hydrogen bond networks with water molecules, creating a highly hydrated gel-like film on the stratum corneum surface that retards TEWL and maintains surface moisture. Due to its high molecular weight, it does not penetrate significantly into the epidermis but acts as a surface-active moisture reservoir. Critically, γ-PGA competitively inhibits hyaluronidase (the enzyme that degrades hyaluronic acid) by binding to the enzyme's active site, preserving endogenous HA in the dermal extracellular matrix. This results in sustained dermal hydration and improved skin plumpness over time. γ-PGA also enhances the moisturizing effects of co-formulated humectants (glycerin, HA) by creating a moisture-trapping surface layer. Additionally, it promotes fibroblast proliferation and increases natural moisturizing factor (NMF) production in keratinocytes.
Indications
- Dry skin / xerosis
- Dehydrated and aging skin
- Fine lines and wrinkles (hydration-related)
- Photoaging
- Barrier support (surface moisture film)
- Sensitive skin hydration
- Hyaluronic acid preservation
Available Concentrations
Side Effects
- Extremely well tolerated
- No significant irritation, sensitization, or phototoxicity reported
- May leave a slight film or tackiness at high concentrations
- Rare individual sensitivity to fermentation-derived ingredients
Contraindications
- Known hypersensitivity to polyglutamic acid or Bacillus subtilis-derived fermentation products
- Soy allergy (if fermentation substrate includes soy — check source)
Pregnancy Category
Not classified (generally considered safe — naturally derived biopolymer with no systemic absorption)