fosfopeptidejä

fosfopeptidejä (phosphopeptides) are short chains of amino acids that contain one or more phosphorylated residues, usually serine, threonine or tyrosine. The phosphorylation is carried out by protein kinases or lipid kinases and constitutes a major post‑translational modification that regulates protein function, localisation, and interactions. Because only a small portion of a protein is needed for many functional studies, phosphopeptides are commonly used in biochemical assays and high‑throughput proteomic screens.

In proteomic workflows, proteins are digested with a protease such as trypsin to generate peptides. Enrichment methods – metal‑oxide affinity, immobilised metal affinity chromatography, or titanium‑dioxide chromatography – are then applied to isolate phosphopeptides from the complex mixture. The enriched sample is analysed by liquid‑phase liquid chromatography coupled with tandem mass spectrometry (LC‑MS/MS). Fragmentation spectra provide site‑specific information that allows the precise determination of phosphorylation sites and stoichiometry.

Phosphopeptides are indispensable for understanding signal transduction pathways. For example, the MAPK pathway relies on sequential phosphorylation events that can be monitored through specific phosphopeptide signatures. In addition, phosphopeptide profiling enables biomarker discovery in diseases such as cancer, where aberrant phosphorylation patterns are common.

Beyond signaling, phosphopeptides can serve as therapeutic leads. Phosphomimetics, compounds that mimic the negative charge of the phosphate group, are being explored as inhibitors of kinase activity. Synthetic phosphopeptides are also used as vaccine antigens, especially in peptide‑based immunotherapies.

Overall, fosfopeptidejä provide a powerful, versatile lens for dissecting cellular regulation, diagnosing disease, and guiding drug development.