<Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (December 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> The enzymes that are secreted in the stomach are gastric enzymes . The stomach plays a major role in digestion, both in a mechanical sense by mixing and crushing the food, and also in an enzymatic sense, by digesting it . The following are enzymes produced by the stomach and their respective function: </P> <Ul> <Li> Pepsin is the main gastric enzyme . It is produced by the stomach cells called "chief cells" in its inactive form pepsinogen, which is a zymogen . Pepsinogen is then activated by the stomach acid into its active form, pepsin . Pepsin breaks down the protein in the food into smaller particles, such as peptide fragments and amino acids . Protein digestion, therefore, first starts in the stomach, unlike carbohydrate and lipids, which start their digestion in the mouth . </Li> <Li> Gastric lipase: Gastric lipase is an acidic lipase secreted by the gastric chief cells in the fundic mucosa in the stomach . It has a pH optimum of 3--6 . Gastric lipase, together with lingual lipase, comprise the two acidic lipases . These lipases, unlike alkaline lipases (such as pancreatic lipase), do not require bile acid or colipase for optimal enzymatic activity . Acidic lipases make up 30% of lipid hydrolysis occurring during digestion in the human adult, with gastric lipase contributing the most of the two acidic lipases . In neonates, acidic lipases are much more important, providing up to 50% of total lipolytic activity . </Li> </Ul> <Li> Pepsin is the main gastric enzyme . It is produced by the stomach cells called "chief cells" in its inactive form pepsinogen, which is a zymogen . Pepsinogen is then activated by the stomach acid into its active form, pepsin . Pepsin breaks down the protein in the food into smaller particles, such as peptide fragments and amino acids . Protein digestion, therefore, first starts in the stomach, unlike carbohydrate and lipids, which start their digestion in the mouth . </Li>

What plays a key role in digestion by secreting various enzymes that digest four types of food