PSP (Polysaccharopeptide)

PSP (Polysaccharopeptide) is a protein-bound polysaccharide extracted primarily from Trametes versicolor (Turkey Tail mushroom, Coriolus versicolor). It is not a traditional macronutrient source but rather a bioactive glycoprotein complex. Key compositional details: **Polysaccharide component (~90-95% of dry weight of the extract):** predominantly beta-glucans (β-1,3 and β-1,4 glucans) with molecular weights ranging from 100–200 kDa, which are responsible for much of the immunomodulatory activity. **Peptide/protein component (~5-10%):** contains a small polypeptide moiety rich in aspartic acid, glutamic acid, and serine, covalently bonded to the polysaccharide backbone, distinguishing PSP from the related compound PSK (Krestin). **Monosaccharide composition:** glucose (dominant), galactose, mannose, xylose, fucose, and arabinose in varying ratios. **Trace minerals:** contains small amounts of potassium (≈1.2–2.0 mg/g), iron (≈0.05–0.15 mg/g), zinc (≈0.02–0.08 mg/g), selenium (≈0.001–0.003 mg/g), and manganese (≈0.01–0.04 mg/g), depending on cultivation substrate. **Fiber:** the beta-glucan content itself functions as soluble dietary fiber, typically comprising 30–45% of the crude extract. **Vitamins:** negligible vitamin content in purified PSP extracts; however, whole Turkey Tail mushroom powders from which PSP is derived may contain small amounts of B-vitamins (B1, B2, B3, B5) and ergosterol (provitamin D2, ~0.01–0.05 mg/g). **Bioactive secondary compounds:** trace amounts of sterols (ergosterol), triterpenes, and phenolic compounds contributing mild antioxidant activity (ORAC values vary by extraction method). **Caloric content:** negligible when consumed at standard supplemental doses (1–3 g/day). **Bioavailability notes:** Oral bioavailability of beta-glucans in PSP is moderate; the protein-bound nature of PSP enhances water solubility and gastrointestinal absorption compared to free polysaccharides. Beta-glucans are recognized by Dectin-1 and complement receptor 3 (CR3) on immune cells in gut-associated lymphoid tissue (GALT) and Peyer's patches, facilitating systemic immune activation even without full systemic absorption. The peptide moiety may improve resistance to gastric degradation. Standardized extracts typically provide ≥40% polysaccharides per dose. Typical supplemental dosing in clinical studies ranges from 1–3 g/day of PSP extract.