Gastric LipaseEdit
Gastric lipase is a digestive enzyme produced by the stomach, primarily secreted by the gastric glands of the fundic region. Alongside other components of gastric juice, it contributes to the initial hydrolysis of dietary triglycerides as food passes through the stomach. Although its overall contribution to fat digestion in healthy adults is modest compared with the pancreatic lipase system, gastric lipase plays a meaningful role in early fat processing, and it is especially important in infants who rely more on gastric and lingual lipases to break down milk fats before the full suite of intestinal lipases becomes dominant.
In humans, gastric lipase is encoded by the LIPF gene and operates in the acidic environment of the stomach. Its activity is optimized at low pH and tends to diminish as the chyme enters the duodenum, where bile salts and pancreatic enzymes take on the principal burden of triglyceride digestion. Gastric lipase commonly acts on triglycerides to produce diacylglycerol and a free fatty acid, contributing to the production of absorbed lipid fragments early in the digestive process. Its action complements other lipases such as lipase enzymes and is part of the broader system that handles dietary fats, including interactions with emulsification processes and the eventual formation of micelles for intestinal uptake.
Biochemical properties
Enzyme class and origin
Gastric lipase is a serine hydrolase secreted by the stomach. It shares functional similarities with other lipases that catalyze the hydrolysis of triglycerides, but it is adapted to the gastric environment and does not rely on the same cofactors as pancreatic lipase under many circumstances. The enzyme is released into the lumen of the stomach as part of the mixed gastric juice that accompanies meals.
Substrates and reaction
The canonical reaction involves the hydrolysis of triglycerides (fats) into diacylglycerol and a free fatty acid. In practice, the enzyme shows a preference for certain fatty acid chains, and it tends to contribute more significantly to the digestion of short- and medium-chain fatty acids, particularly those present in milk fat and certain dietary fats consumed in the stomach. The overall outcome is an early, partial breakdown of fat that feeds into subsequent intestinal lipolysis.
pH dependence and conditions
Gastric lipase operates best in the acidic milieu of the stomach, where the primary pH is low. Its activity declines as chyme mixes with alkaline secretions in the small intestine, and pancreatic lipase becomes the dominant force for triglyceride digestion. The gastric environment, including acidity and mechanical churning, influences the efficiency of gastric lipase by shaping substrate availability and emulsification status early in digestion.
Interaction with other lipases and emulsification
The digestive process relies on a coordinated sequence of lipolysis. Gastric lipase works alongside lingual lipase (secreted in the mouth) and later with pancreatic lipase in the small intestine. Although pancreatic lipase accounts for most triglyceride hydrolysis in the small intestine, gastric lipase provides an initial step that can influence the timing and distribution of fatty acids entering the intestinal lumen. Emulsification, aided by bile and mechanical mixing, enhances the accessibility of triglycerides to lipases across the digestive tract.
Physiological role
infancy and early digestion
In newborns and young infants, gastric lipase and lingual lipase together contribute substantially to the digestion of breast milk and formula fats. Milk fats contain triglycerides with fatty acids that are more amenable to hydrolysis by these enzymes in the gastric and oral environments. This early lipolysis supports energy production during a critical growth period when efficient fat absorption is essential.
adult digestion
In healthy adults, the majority of triglyceride digestion occurs in the small intestine, driven by pancreatic lipase with assistance from cofactor proteins and bile salts. Gastric lipase still participates, but its relative contribution is smaller, serving as an initial hydrolytic step that precedes intestinal processing. The stomach’s mechanical digestion—stirring and mixing with gastric juice—also helps distribute fat molecules so that later enzymes can act more effectively.
clinical considerations
Gastric lipase activity can be influenced by gastric pH and mucosal integrity. Conditions that reduce acid secretion or damage the gastric lining may alter the enzyme’s effectiveness. In the context of pancreatic insufficiency or disorders of fat digestion, the gastric lipase pathway may become relatively more important, though it cannot fully compensate for impaired pancreatic lipase activity. Genetic variation in the LIPF gene can influence enzyme expression levels or activity, contributing to interindividual differences in fat digestion efficiency. Research into the precise quantitative role of gastric lipase across populations continues, with some studies suggesting a measurable, though secondary, contribution to overall fat hydrolysis in adults and a more prominent role in early life.
Genetic and comparative aspects
Gastric lipase is encoded by the LIPF gene in humans, a component of the exocrine pancreas−stomach axis that governs lipolysis in the digestive tract. Across mammals, gastric lipase and related lipases exhibit evolutionary optimization to handle species-specific fat sources and dietary patterns, reflecting the balance between digestive enzymes produced in the stomach and those secreted by the pancreas. Comparative studies highlight a spectrum of reliance on gastric versus pancreatic lipases, with variations tied to feeding strategies, stomach physiology, and bile salt exposure.