Labeling-Based Quantitative Phosphoproteomics: TMT, iTRAQ, SILAC, and Enrichment Strategies

Published: May 20, 2026

Labeling-based quantitative phosphoproteomics cover

Phosphorylation often changes before total protein abundance shifts. Labeling-based quantification, TMT, iTRAQ, or SILAC, multiplexes conditions when phosphopeptide enrichment and MS settings match phosphoproteome stoichiometry.

Key Takeaways

Phosphopeptides are <1% of peptides; enrichment is standard.
TMT multiplexes many conditions; manage ratio compression.
iTRAQ suits defined control-treatment designs.
SILAC fits cell culture kinetics, not most tissues.
Dual enrichment can deepen site coverage.

Phosphoproteomics labeling workflow — Figure 1. Enrichment quality dominates sensitivity.

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TMT, iTRAQ, and SILAC

Label	Multiplex	Best fit
TMT	High plex	Large panels, time courses
iTRAQ	Up to 8	Defined comparisons
SILAC	2–3 states	Cell culture kinetics

Phosphopeptide enrichment — Figure 2. Match enrichment to sample complexity.

Applications

TMT for multi-condition screens; iTRAQ for moderate cohorts; SILAC for stimulation time courses in cells.

Method selection — Figure 3. Sample type dictates SILAC feasibility.

FAQ

Why is enrichment mandatory?

Low phosphopeptide stoichiometry hides sites without enrichment.

Conclusion

Match label chemistry to sample type and invest in phosphopeptide capture for reliable quantitative phosphoproteomics.

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