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Saliva on a baby's lips. Saliva (commonly referred to as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth.In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (such as lipase and amylase), and antimicrobial agents (such as secretory IgA, and lysozymes).
α-Amylase is an enzyme (EC 3.2.1.1; systematic name 4-α-D-glucan glucanohydrolase) that hydrolyses α bonds of large, α-linked polysaccharides, such as starch and glycogen, yielding shorter chains thereof, dextrins, and maltose, through the following biochemical process: [2]
In animals, it is a major digestive enzyme, and its optimum pH is 6.7–7.0. [3] In human physiology, both the salivary and pancreatic amylases are α-amylases. The α-amylase form is also found in plants, fungi (ascomycetes and basidiomycetes) and bacteria .
As a result, saliva allows some digestion to occur before the food reaches the stomach. [30] Taste: [31] Saliva acts as a solvent in which solid particles can dissolve and enter the taste buds through oral mucosa located on the tongue. These taste buds are found within foliate and circumvallate papillae, where minor salivary glands secrete ...
Function: An enzyme that is produced by animals that forms part of the innate immune system and is abundant in the secretions of saliva, human milk, tears, and mucus. It functions as an antimicrobial agent by splitting the peptidoglycan component of bacterial cell walls, which then leads to cell death. Clinical Significance: Toxic levels of ...
Also of importance is the presence in saliva of the digestive enzymes amylase and lipase. Amylase starts to work on the starch in carbohydrates, breaking it down into the simple sugars of maltose and dextrose that can be further broken down in the small intestine. Saliva in the mouth can account for 30% of this initial starch digestion.
Beyond β-glucosidases expressed in human tissues, bacterial β-glucosidases are also found in human saliva and inside the intestine produced by the bacterial microbiota of the mouth and gastro-intestinal tract, with various implications to normal human health, drug and hormone metabolism, and involvement in certain diseases. [11] [12]
Seromucous glands (mixed) secrete both protein and mucus. Examples include the salivary glands: although the parotid gland (saliva secretion 25%) is predominantly serous, the sublingual gland (saliva secretion 5%) mainly mucous gland, and the submandibular gland (saliva secretion 70%) is a mixed, mainly serous gland.