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What Enzyme is released by the Stomach to Digest Protein?

Let’s get one thing straight: proteins are one of the most important substances in the human body. Your hair, eyes, muscles, organs, many hormones and enzymes are mostly made up of proteins. When your body tissues need to be repaired or maintenance, proteins are highly involved.

But, not all proteins are the same, nor are they created in the same way. Overall, a protein is a nutrient that is made of a component called amino acids. Your body can produce nine amino acids, however, you will find that we have twenty different types of amino acids inside us. The eleven amino acids that we can’t produce ourselves are called essential amino acids and we get them through our diet

There are many sources of proteins around, but only the high quality sources, for example meat, fish, eggs, and dairy products, have all the essential amino acids. We really need those, and they’re also known as whole or complete proteins.

The other well-known protein sources, like beans, nuts, and seeds, only contain some of those amino acids. However, if you combine two or three of those, you can still get the essential amino acids, for example a plate with rice and beans will create a whole protei

Enzymes and digestion

The moment you start chewing your food, the entire digestion begins. Our saliva has two very important enzymes; amylase and lipase. These, however, don’t play a role in protein digestion, they work with carbohydrates and fats. When it comes to protein digestion, it really begins in the stomach, not the mouth.

When the protein that you’re eating actually reaches your stomach, then it begins the digestive process for it. First the hydrochloric acid and a group of enzymes called proteases break it down into chains of amino acids that are much smaller. Of these enzymes, the most abundant one is called Pepsin. It is considered the main gastric enzyme. It is produced by the stomach cells and its inactive form is known as pepsinogen. When the stomach acids come into play, pepsinogen is then activated into pepsin.

This enzyme is very important because it’s the one that actually breaks down the long protein chains into smaller particles, like peptide fragments and shorter chains of amino acids.

Another important enzyme produced in the stomach is called Gastric Lipase, it is an acidic enzyme with a pH optimum of 3-6. Acidic lipases are the ones responsible for around 30% of lipid hydrolysis in the digestion process in humans.

Once pepsin has done its work, these smaller chains of amino acids then move from the stomach into the small intestine. At the same time, the pancreas releases a group of enzymes and a buffer with bicarbonate so that the acidity level decreases, allowing more enzymes to work in a convenient environment so that they can break down those amino acid chains even more, into individual amino acids.

In this stage of the protein digestion, some of the enzymes include:

  • Trypsin
  • Chymotrypsin
  • Carboxypeptidase

The small intestine is the place where protein absorption really occurs thanks to the microvilli. These finger-like structures allow the surface area of the intestine to increase, resulting in a better absorption rate of amino acids and other nutrients too.