Novel Post-translational Modifications in Human Serum Albumin

Aim: This study aims to identify novel post-translational modifications in human serum albumin by mass spectrometry. Background: Serum albumin is the most abundant protein in plasma, has many physiological functions, and is in contact with most of the cells and tissues of the human body. Post-translational modifications (PTMs) may affect functions, stability, and localization of albumin. Methods: Human serum albumin (HSA) was used for tryptic digestion in-solution or in-gel. Mass spectrometry was applied to identify PTMs in HSA. 3-dimensional modeling was applied to explore the potential impact of PTMs on known functions of albumin. Results: Here, we report the identification of 61 novel PTMs of human serum albumin. Phosphorylation, glycosylation, nitrosylation, deamidation, methylation, acetylation, palmitoylation, geranylation, and farnesylation are some examples of the identified PTMs. Mass spectrometry was used for the identification of PTMs in a purified HSA and HSA from the human plasma. Threedimensional modeling of albumin with selected PTMs showed the location of these PTMs in the regions involved in albumin interactions with drugs, metals, and fatty acids. The location of PTMs in these regions may modify the binding capacity of albumin. Conclusion: This report adds 61 novel PTMs to the catalog of human albumin.