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Mannosidase production by viridans group streptococci
K A Homer1, G Roberts, H L Byers
1Department of Oral Microbiology, GKT Dental Institute, King's College London, Caldecot Rd., Denmark Hill, London SE5 9RW, United Kingdom. karen.a.homer@kcl.ac.uk
Journal of Clinical Microbiology
|March 7, 2001
Summary
Mannosidase activity, crucial for utilizing mannose from RNase B glycans, is present in more viridans group streptococci species than previously known. This enzyme
Area of Science:
- Microbiology
- Glycobiology
- Bacterial Enzymology
Background:
- Viridans group streptococci are common human commensals.
- Mannosidase enzymes are involved in carbohydrate metabolism.
- Previous understanding of mannosidase production in these bacteria was limited.
Purpose of the Study:
- To determine the prevalence of mannosidase activity across human viridans group streptococci species.
- To investigate the substrate specificity of streptococcal mannosidases using a native glycoprotein.
- To compare mannosidase activity on a native glycoprotein versus synthetic substrates.
Main Methods:
- Bacterial growth-dependent assay utilizing RNase B high-mannose-type glycans.
- Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) for glycan analysis.
- Enzyme activity assays with synthetic alpha- and beta-mannosides.
Main Results:
- Mannosidase activity was detected in some mitis group species (S. mitis, S. oralis, S. gordonii, S. cristatus, S. infantis, S. parasanguinis, S. pneumoniae) and Streptococcus intermedius (anginosus group).
- Only Man(5) glycan from RNase B was degraded; larger glycans remained intact.
- No correlation was found between degradation of synthetic mannosides and RNase B glycan. Alpha-mannosides were not degraded, while beta-mannosides were degraded by limited strains.
Conclusions:
- Mannosidase production is more widespread in viridans group streptococci than previously recognized.
- The enzyme preferentially degrades specific high-mannose structures (Man(5)) from RNase B.
- Synthetic substrates do not accurately reflect the activity of mannosidases on native glycoproteins.