Polysaccharide-K

Polysaccharide-K (Krestin, PSK) is a protein-bound polysaccharide isolated from the mycelium[1][2] of Trametes versicolor.

PSK is one of the most commonly used medicinal mushroom extracts with a long history as an additive in cancer therapy in Asia, especially in Japan.

PSK has adjuvant anti-tumor activity in vitro in various types of cancers, including colorectal, gastric, breast, liver, pancreatic, and lung cancer.

The approximate molecular weight of PSK is 100,000 Da, and the protein component is reported at the β-1,6 side chain.

The analogous compound PSP, is derived from the "COV-1" strain of Trametes versicolor.

Trametes versicolor , the mushroom from which PSK was isolated.