Lingual lipase
Lingual lipase is a fat-digesting enzyme secreted by glands of the tongue. It begins triglyceride breakdown in the mouth and, because it works best at acidic pH, continues acting in the stomach.
Lingual lipase is a lipolytic enzyme secreted in the mouth, classically attributed to the serous von Ebner's glands of the tongue. It initiates the digestion of dietary fat by hydrolyzing triglycerides into diglycerides and free fatty acids, making it one of the first digestive enzymes food encounters — alongside salivary amylase, which starts carbohydrate digestion.
What sets lingual lipase apart is its acidic pH optimum. Unlike most salivary enzymes, it is not inactivated by stomach acid; in fact, much of its activity occurs after the food bolus is swallowed, as the enzyme keeps working in the acidic environment of the stomach. There it operates alongside gastric lipase, and together these "acid lipases" handle the early, pancreatic-independent phase of fat digestion.
In healthy adults, the overwhelming majority of fat digestion is carried out by pancreatic lipase in the small intestine, so lingual lipase plays a supporting role. It matters most in neonates, whose pancreatic function is immature — acid lipases help infants digest milk fat — and it becomes more relevant in conditions of pancreatic insufficiency, such as cystic fibrosis or chronic pancreatitis.
For exam purposes, lingual lipase is a classic detail in gastrointestinal physiology. USMLE Step 1 tests where each digestive enzyme originates and acts — remember that lingual lipase starts fat digestion in the mouth, survives gastric acid, and is distinct from both salivary amylase and pancreatic lipase.
Key takeaways
- Lingual lipase is secreted by von Ebner's glands of the tongue and begins triglyceride digestion in the mouth.
- It hydrolyzes triglycerides into diglycerides and free fatty acids.
- Its acidic pH optimum lets it remain active in the stomach, unlike most salivary enzymes.
- It is most important in neonates and in patients with pancreatic insufficiency; pancreatic lipase dominates fat digestion in healthy adults.
- USMLE Step 1 tests lingual lipase within the lineup of GI enzymes and their sites of action.