Chemoenzymatic synthesis of Neu5Ac9NAc-containing α2–3- and α2–6-linked sialosides and their use for sialidase substrate specificity studies

Wanqing Li, An Xiao, Yanhong Li, Hai Yu, Xi Chen

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


O-Acetylation of sialic acid (Sia) modulates its recognition by sialic acid-binding proteins and plays an important role in biological and pathological processes. 9-O-Acetylation is the most common modification of sialic acid in human. However, study of O-acetylated sialoglycans is hampered due to the instability of O-acetyl group towards pH changes and sensitivity to esterases. Our previous studies demonstrated a chemical biology method to this problem by replacing the oxygen atom in the C9 ester group of sialic acid by a nitrogen to form an amide. Here, we synthesized a library of sixteen new 9-acetamido-9-deoxy-N-acetylneuraminic acid (Neu5Ac9NAc)-containing α2–3- and α2–6-linked sialosides with various underlying glycans using efficient one-pot three-enzyme (OP3E) sialylation systems. Neu5Ac9NAc-containing compounds with a para-nitrophenol aglycon have been used together with their 9-O-acetyl analogs in microtiter plate-based high-throughput substrate specificity studies of nine different sialidases including those from humans and bacteria. In general, similar to 9-O-acetylation, 9-N-acetyl modification of sialic acid in the substrates lowers sialic acid-cleavage activity of most sialidases. In most cases, Neu5Ac9NAc is a good analog of 9-O-acetyl sialic acid. However, exceptions do exist. For example, 9-N- and 9-O-acetyl modifications have different effects on the sialosides cleave efficiencies of a commercially available C. perfringens sialidase as well as recombinant Streptococcus pneumoniae sialidase SpNanC and Bifidobacterium infantis sialidase BiNanH2. The mechanism for the difference awaits further investigation.

Original languageEnglish (US)
Pages (from-to)51-58
Number of pages8
JournalCarbohydrate Research
StatePublished - Nov 8 2017


  • 9-N-acetyl sialic acid
  • 9-O-acetyl sialic acid
  • Chemoenzymatic synthesis
  • One-pot multienzyme
  • Sialic acid

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Organic Chemistry


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