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Updated: Jun 3, 2026

Protease- and Acid-catalyzed Labeling Workflows Employing 18O-enriched Water
Published on: February 20, 2013
Mass spectrum patterns of 18O-tagged peptides labeled by enzyme-catalyzed oxygen exchange
1Bioinformatics Department, Center for Genetic Engineering and Biotechnology, P.O. Box 6162, CP 10600, C. Habana, Cuba. jorge.cossio@cigb.edu.cu
Abstract:
(18)O-labeling of peptides is a technique widely and routinely applied in the protein chemistry laboratories. The rate of (18)O incorporation at the carboxyl terminus of peptides via enzyme-catalyzed oxygen exchange fluctuates from peptide to peptide. This fluctuation is mostly attributed to enzyme-substrate different affinity. The final distributions of the (18)O(0)-, (18)O(1)-, and (18)O(2)-tagged peptides remain unpredictable though usually constrained to binomial proportions. It is proved here that this constraint can sometimes be a poor model. A more general model is then derived which predicts linear paths for digestion in H(2)(18)O-enriched water while confining binomial proportions to postdigestion labeling. Both subderived models are simple in structure and relevant for the current software development in the analysis of quantitative shotgun proteomics data. Accuracy and time dependency are examined and compared with actual labeled-digest data.
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