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Updated: Jun 1, 2026
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Published on: July 14, 2017
NeuA O-acetylesterase activity is specific for CMP-activated O-acetyl sialic acid in Streptococcus suis serotype 2
Lili Song1, Hui Zhou, Xuehui Cai
1Key Laboratory of Systematic Mycology and Lichenology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
Abstract:
Several bacteria causing meningitis, such as Escherichia coli K1, Streptococcus suis, Neisseria meningitidis, and group B Streptococci (GBS), produce sialic acid (Neu5Ac)-containing capsular polysaccharide (CPS). Biosynthesis of the Neu5Ac-containing CPS requires CMP-Neu5Ac as substrate, which is synthesized by CMP-Neu5Ac synthetase from CTP and Neu5Ac. In E. coli or GBS, the NeuA protein encoded by the neuA gene has been known encoding a bifunctional enzyme that possesses both CMP-Neu5Ac synthetase and O-acetylesterase activity. In this report, we found that the S. suis NeuA (SsNeuA) was also a bifunctional CMP-Neu5Ac synthetase/O-acetylesterase. Biochemical analyses revealed that the SsNeuA strictly de-O-acetylated CMP-O-acetyl-Neu5Ac, whereas the E. coli NeuA (EcNeuA) preferentially de-O-acetylated CMP-O-acetyl-Neu5Ac. E. coli devoid of NeuA O-acetylesterase activity was unable to produce capsule and only CMP-Neu5Ac synthetase activity of the EcNeuA or SsNeuA could not restore its ability to produce capsule. These results suggest that the O-acetylesterase is essential for the synthesis of capsular Neu5Ac in E. coli, probably in S. suis and GBS as well. Our findings are key to understanding the biosynthesis of capsular Neu5Ac in E. coli, S. suis and GBS.
Insights
The O-acetylesterase activity of NeuA is essential for capsular sialic acid (Neu5Ac) synthesis in bacteria like E. coli. This finding is crucial for understanding capsule production in meningitis-causing bacteria.
Area of Science:
- Microbiology
- Biochemistry
- Bacterial Pathogenesis
Background:
- Meningitis-causing bacteria like E. coli, S. suis, N. meningitidis, and GBS synthesize sialic acid (Neu5Ac)-containing capsular polysaccharide (CPS).
- CPS biosynthesis relies on CMP-Neu5Ac, produced by CMP-Neu5Ac synthetase from CTP and Neu5Ac.
- The NeuA protein in E. coli and GBS is a known bifunctional enzyme with CMP-Neu5Ac synthetase and O-acetylesterase activities.
Purpose of the Study:
- To investigate the enzymatic activities of Streptococcus suis NeuA (SsNeuA) and its role in capsular polysaccharide synthesis.
- To compare the O-acetylesterase activity of SsNeuA with that of E. coli NeuA (EcNeuA).
- To determine the essentiality of NeuA's O-acetylesterase activity for capsular Neu5Ac production in E. coli.
Main Methods:
- Biochemical analyses were performed to characterize the enzymatic activities of SsNeuA and EcNeuA.
- Enzyme assays focused on CMP-Neu5Ac synthetase and O-acetylesterase activities.
- Genetic manipulation of E. coli was used to create strains lacking NeuA O-acetylesterase activity and to assess capsule production.
Main Results:
- SsNeuA was confirmed as a bifunctional CMP-Neu5Ac synthetase/O-acetylesterase.
- SsNeuA strictly de-O-acetylated CMP-O-acetyl-Neu5Ac, while EcNeuA preferentially performed this reaction.
- E. coli lacking NeuA O-acetylesterase activity could not produce capsules, and only CMP-Neu5Ac synthetase activity was insufficient to restore capsule production.
Conclusions:
- The O-acetylesterase activity of NeuA is essential for the synthesis of capsular Neu5Ac in E. coli.
- This finding likely extends to other bacteria such as S. suis and GBS.
- The study provides critical insights into the biosynthesis of capsular Neu5Ac in key bacterial pathogens.
