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Terminal glycosylation in human cervical mucin
Ciba Foundation Symposium
|January 1, 1984
Summary
L-fucose levels in cervical mucin are more tightly regulated than N-acetylneuraminic acid due to enzyme activity and removal processes. This suggests distinct regulatory mechanisms control mucin glycosylation.
Area of Science:
- Biochemistry
- Glycobiology
- Reproductive Biology
Background:
- L-fucose and N-acetylneuraminic acid are terminal monosaccharides on human cervical mucin oligosaccharides.
- Simultaneous addition of both monosaccharides to the same residue is kinetically unfavorable.
Purpose of the Study:
- To investigate the differential regulation of L-fucose and N-acetylneuraminic acid incorporation into cervical mucin.
- To explore the enzymatic and environmental factors influencing mucin glycosylation and rheology.
Main Methods:
- Enzyme activity assays for sialyltransferase (EC 2.4.99.1) and fucosyltransferase (EC 2.4.1.68).
- Analysis of enzyme inhibition kinetics (Ki and Km).
- Autoradiography using [3H]L-fucose on cervical explants in organ culture.
- Assessment of mucus production sensitivity to ovarian steroid hormones.
Main Results:
- Sialyltransferase activity is 20-30 times higher than fucosyltransferase activity.
- Fucosyltransferase is more susceptible to product inhibition, suggesting greater regulatory control.
- High levels of mucus-associated alpha-L-fucosidase likely mediate post-secretory L-fucose removal, potentially modulated by cervical pH.
- Mucus production in organ culture is insensitive to exogenous ovarian steroid hormones.
Conclusions:
- L-fucose incorporation into cervical mucin appears more tightly regulated than N-acetylneuraminic acid.
- Mucin glycosylation and rheology cyclicity may not be directly influenced by ovarian steroid hormones acting on synthesis or hydration.