Distinct <i>O</i>‑Acetylation Patterns\nof Serum Glycoproteins among Humans, Mice, and Rats

<i>O</i>-Acetylation is a significant chemical\nmodification\nof sialic acids on glycoproteins with diverse biological functions.\nAs two important animal models, mice and rats have been widely used\nfor various biomedical studies. In this study, we show that the sialic\nacid types and their <i>O</i>-acetylation patterns have\nlarge differences among serum glycoproteins of humans, rats, and mice.\nBased on intact <i>N</i>-glycopeptide analyses, all sialoglycopeptides\nin human sera were modified by Neu5Ac without any <i>O</i>-acetylation; 90% of sialoglycopeptides in rat sera were also modified\nby Neu5Ac, with more than 60% that were further <i>O</i>-acetylated. In contrast, 99% of sialoglycopeptides in mouse sera\ncontained Neu5Gc including 12% in <i>O</i>-acetylated forms.\nAmong all <i>O</i>-acetylated <i>N</i>-glycans,\nrat sera had hybrid glycans fivefold those of mouse sera, while mouse\nsera contained 5.5-fold core-fucosylated glycans and 4.6–31.5-fold\nmono-/penta-/hexa-antenna glycans compared to mice. The overall <i>O</i>-acetylation proportions of serum glycoproteins in rats\nwere much higher than those in mice, and diverse <i>O</i>-acetylation proportions also commonly existed at different glycosites\nof the same glycoproteins. This study enhances our understanding of <i>O</i>-acetylated sialoglycan diversities and underscores the\nnecessity of considering glycosylation profiles when selecting suitable\nanimal models for various biomedical studies.