Concept: Salivary glands are exocrine glands that produce saliva, which is secreted into the mouth. Saliva plays roles in lubrication, taste, and the initial stages of digestion, primarily due to the presence of specific enzymes. Step 1: Primary Digestive Enzyme in Saliva
The main digestive enzyme present in human saliva is salivary amylase (also known by an older name, ptyalin).
Salivary amylase initiates the chemical digestion of carbohydrates, specifically breaking down starch (a complex polysaccharide) into smaller sugar molecules like maltose (a disaccharide) and dextrins. Step 2: Analyzing the options
(1) Lipase: Lipases are enzymes that digest fats (lipids) into fatty acids and glycerol. While a very small amount of {lingual lipase} (secreted by glands on the tongue, not primarily the major salivary glands) may be present in saliva and begin some fat digestion, the predominant and characteristic digestive enzyme of the salivary glands for carbohydrate digestion is amylase.
(2) Amylase: Correct. Salivary glands produce salivary amylase, which acts on starch.
(3) Lyase: Lyases are a class of enzymes that catalyze the breaking of various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure. This is a general enzyme category, not specific to salivary digestion.
(4) Peptidase (or Protease): Peptidases are enzymes that break down proteins or peptides into smaller peptides or amino acids. Examples include pepsin (in the stomach) and trypsin (in the small intestine). Saliva does not contain significant peptidase activity for protein digestion. Therefore, the primary enzyme relevant to digestion found in saliva produced by salivary glands is amylase.