Arginine is abundant in which of the following in the oral environment?

• A. Salivary peptides and proteins
• B. Dental plaque
• C. Saliva
• D. Epithelium

Answer: (A)

Arginine is abundant in salivary peptides and proteins because saliva contains a wide array of secreted proteins and peptides that include arginine residues in their amino acid sequences. These host proteins are continually released into the oral environment, providing a rich pool of arginine that oral bacteria can access. This is important because many oral bacteria metabolize arginine via the arginine deiminase system to produce ammonia, which raises local pH and buffers acids produced by sugar-fermenting bacteria, helping protect against demineralization. While arginine can be present in other oral components, the salivary protein/peptide fraction is the most substantial and readily available source in the mouth, making salivary peptides and proteins the best answer.