Polysaccharide-K (Krestin, PSK) is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
-bound
polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wat ...
isolated from the mycelium
of ''
Trametes versicolor
''Trametes versicolor''also known as ''Coriolus versicolor'' and ''Polyporus versicolor''is a common polypore mushroom found throughout the world. Owing to its shape being similar to that of a wild turkey's tail feathers, ''T. versicolor ...
''.
Research
PSK is one of the most commonly used medicinal mushroom extracts with a long history as an additive in
cancer
Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...
therapy in Asia, especially in
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
. PSK has
adjuvant
In pharmacology, an adjuvant is a drug or other substance, or a combination of substances, that is used to increase the efficacy or potency of certain drugs. Specifically, the term can refer to:
* Adjuvant therapy in cancer management
* Anal ...
anti-tumor activity ''
in vitro
''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...
'' in various types of cancers, including colorectal, gastric, breast, liver, pancreatic, and lung cancer.
Preliminary studies examining PSK include its use in conjunction with
chemotherapy
Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...
for colorectal cancer.
Chemistry
PSK is a protein polysaccharide consisting of a
beta-glucan
Beta-glucans, β-glucans comprise a group of β-D-glucose polysaccharides ( glucans) naturally occurring in the cell walls of cereals, bacteria, and fungi, with significantly differing physicochemical properties dependent on source. Typically, ...
β-1,4 main chain with β-1,3 and β-1,6 side chains. The approximate molecular weight of PSK is 100,000
Da, and the protein component is reported at the β-1,6 side chain.
PSK is isolated from the "CM-101" strain of ''Trametes versicolor''. The analogous compound
PSP, is derived from the "COV-1" strain of ''Trametes versicolor''.
See also
*
Medicinal mushrooms
Medicinal fungi are fungi that contain metabolites or can be induced to produce metabolites through biotechnology to develop prescription drugs. Compounds successfully developed into drugs or under research include those treating infection with am ...
*
Polysaccharide peptide
References
{{Reflist, 2
External links
*American Cancer Society's page fo
''Trametes versicolor'' and Polysaccharide-K
*Memorial Sloan-Kettering Cancer Center's page fo
''Trametes versicolor'' and Polysaccharide-K
*
by the MD Anderson Cancer Center.
information from Drugs.com.
Medicinal fungi