Role of Enzymes in Digestion – Part One
The main role of an enzyme is to catalyze or increase the rate of chemical reaction or biological reaction. In digestion, the main function of enzymes is to break down bigger molecules to smaller blocks.
are found in the digestive tract where they are secreted by digestive organs to aid digestion. Digestive enzymes are classified by their substrates, example:
breakdown proteins into amino acids
split fat into fatty acids and glycerol
break carbohydrates into starch and sugars
split nucleic acids into nucleotides
In humans the sources of enzymes are salivary glands in mouth, glands in the stomach, the pancreas and the glands in the small intestine. All the digestive organs of the human body makes approximately
22 different enzymes
that play role in digestion.
Mostly all enzymes are large, complex proteins. They have molecular weights ranging from 10,000 to one million. They are usually soluble and are highly specific.
Many enzymes require an additional non-protein component which are called co-factors. Inorganic ions such as Fe2+, Mn2+, Mg2+, or Zn2+ can also be co-factors for enzymes. The enzymes may also consist of organic or metalloorganic molecules known as co-enzymes.
Actions of digestive enzymes:
The major digestive enzymes and their respective actions are explained as follows:
- Salivary amylase breaks starch and glycerol into sugars.
- Pepsin, the main gastric enzyme, breaks proteins into smaller peptide fragments
- Gastric lipase acts on tributyrin for digestion of fat.
- Gelatinase breaks type 1 and type 5 gelatin and type 4 and type 5 collagen.
- Gastric amylase breaks the starch further into glucose.
- Pancreatic trypsin breaks proteins at the basic amino acids and chymotrypsin cleaves proteins at the aromatic amino acids.
- Pancreatic steapsin converts triglycerides into glycerol and fatty acids.
- Elastases break protein elastin and nucleases break nuclec acids such as DNAase and RNAase.
- In small intestine sucrase cleaves sucrose into glucose and fructose and maltase converts maltose to glucose.
- Simlarly isomaltase converts maltose to glucose and lactase breaks lactose into glucose and galactose. Intestinal lipase cleaves down the fatty acids into smaller particles of fats.