Comparative Analysis of Post-Translational Modifications of Human Serum Albumin Derived from Human Plasma and Recombinant Sources in China.

Background: The variations in sequence, three-dimensional structure, and post-translational modifications (PTMs) of human serum albumin (HSA) are crucial for its physiological functions. This study aims to analyze and compare the disparities in PTMs between HSA derived from human plasma and genetically recombinant sources for clinical treatments in China.

Methods: Six distinct PTMs, namely acetylation, succinylation, crotonylation, phosphorylation, beta-hydroxybutyrylation, and lactylation, were identified using pan-specific antibodies via Western blot analysis. The samples, comprising human plasma-derived HSA (pHSA) from six different manufacturers and recombinant HSA (rHSA) expressed in yeast and , underwent detection for various types of PTMs. Additionally, a 4D label-free quantitative proteomic analysis was performed to identify N-glycosylation and the aforementioned PTMs in both pHSA and rHSA samples. This analysis aimed to discern disparities in modification sites and levels.

Results: Through Western blot analysis, all six pHSA and two rHSA samples displayed positive bands for albumin (66.5 kDa) across the six PTMs. Subsequent analysis using 4D label-free quantitative proteomics revealed 25 (29) acetylated, 30 (32) succinylated, 41 (50) malonylated, 15 (23) phosphorylated, 36 (30) beta-hydroxybutyrylated, and 27 (34) lactylated modification sites in pHSA and rHSA samples, with no N-glycosylation modification sites detected. The analysis identified 1 acetylation (ALB_K160), 2 beta-hydroxybutyrylation (ALB_K569, ALB_K426), and 3 crotonylation (ALB_K264, ALB_K581, ALB_K560) specific modification sites in pHSA, as well as 3 crotonylation (ALB_K560, ALB_K562, ALB_K75), 1 succinylation (ALB_K490), and 23 phosphorylation specific modification sites in rHSA. In pHSA (rHSA), 2 (6) acetylation, 10 (12) succinylation, 0 (9) crotonylation, 1 (9) phosphorylation, 6 (0) beta-hydroxybutyrylation, and 0 (7) lactylation specific modification sites were found. Moreover, in the shared modification sites between pHSA and rHSA, pHSA exhibited up-regulation of amberylation (16:1) and beta-hydroxybutyrylation (12:2) in more sites, and up-regulation of acetylation (7:11), crotonylation (2:11), phosphorylation (1:8), and lactylation (1:14) in fewer sites compared to rHSA.

Conclusion: In clinical practice, both pHSA and rHSA utilized in China commonly display acetylation, succinylation, crotonylation, phosphorylation, beta-hydroxybutyrylation, and lactylation. Notably, there exist distinctions in the site characteristics and modification levels of these alterations between pHSA and rHSA. Further experimental inquiries are imperative to delve into the implications of these disparities in PTMs on the biological functionality, effectiveness, and safety of pHSA and rHSA.