Group 3 glycoproteins include which of the following as examples of neutral glycoproteins?

• A. Ovomucoid (egg white), stomach mucin, Paneth cell granules
• B. Sialomucins
• C. Epithelial mucins
• D. None of the above

Answer: (A)

Neutral glycoproteins are those whose carbohydrate parts do not carry charged groups like sialic acid or sulfate; they lack the acidic components that shift a molecule to a negative charge. Group 3 glycoproteins fall into this neutral category. Ovomucoid from egg white is a classic neutral glycoprotein because its glycan chains are not charged at physiological pH. Stomach mucin is another example of a neutral secreted glycoprotein in the gastric mucus, contributing to the protective layer without adding acidic sugars. Paneth cell granules contain secretory glycoproteins that are also neutral, not relying on sialylation or sulfation for their charge. By contrast, sialomucins contain sialic acid and are acidic, and epithelial mucins often include acidic mucins as well, so they are not neutral Group 3 glycoproteins.