Polyglutamic Acid, an Active Ingredient for Hydrated Skin.

Polyglutamic acid or PGA is a peptide formed from the polymerization of glutamic acid. It is the main ingredient in Nattô, a Japanese dish made from fermented soybeans. Traditionally, PGA was used in medicine to accelerate the healing processes of minor and major injuries and burns. Today, PGA is consumed mainly for its nutritional content. However, recent studies have also looked at its cosmetic benefits. It was found to have excellent moisturizing and soothing properties. Polyglutamic acid is also an effective way to soften the appearance of wrinkles.

This biopolymer combats skin moisture loss at multiple levels:

• Polyglutamic acid is a film-forming agent.

In other words, it forms a microscopic film on the surface of epidermal tissue. This molecular arrangement is called a microgel. It swells upon contact with water and traps the H2O molecules. Thus, polyglutamic acid not only limits transepidermal water loss but also promotes water retention through a moisturizing process. A 2014 study found that PGA has a stronger moisturizing effect than hyaluronic acid. In fact, it is capable of retaining up to 5000 times its weight in water. By comparison, hyaluronic acid stores 1,000 times its weight in water.

• Polyglutamic acid stimulates the production of substances that form the natural moisturizing factor (NMF)

NMF is a group of hygroscopic molecules (amino acids, urea, etc.) formed during epidermal differentiation that bind water in the top layer of the skin. Polyglutamic acid boosts the production of some of these molecules, including pyrrolidone carboxylic acid (PCA), lactic acid, and urocanic acid.

• Polyglutamic acid restricts the activity of hyaluronidase

Hyaluronidase is the enzyme responsible for the breakdown of hyaluronic acid. This molecule is predominantly produced by the fibroblasts of the dermis (deep layer of the skin) and gives the skin its plumped appearance. Hyaluronic acid acts like a molecular sponge and binds water. Over the years, its content decreases: at the age of 50, the supply of hyaluronic acid is said to have decreased by half. This drastic decrease leads to atrophy of the fat pockets in the depth of the dermis, which are responsible for the appearance of wrinkles and fine lines on the skin's surface. By inhibiting the activity of the enzyme hyaluronidase, polyglutamic acid, therefore, prevents skin dehydration and the appearance of signs of aging.

Note: PGA helps maximize the moisture content of the epidermis, but due to its high molecular weight, it cannot act in depth. Its effect is limited to the uppermost layers of the skin. Low molecular weight hyaluronic acid is more recommended to moisturize the skin in depth.