Proteases come from nearly everywhere in the living world. Your own body produces them in the stomach, pancreas, small intestine, and inside every cell. Plants like papaya, pineapple, and kiwi contain their own versions. Bacteria and fungi are the workhorses behind the proteases found in laundry detergent, meat tenderizer, and dietary supplements. Understanding where each type originates helps explain how protein digestion works and what you’re actually getting when you buy a protease product.
Proteases Your Body Makes
Protein digestion starts in your stomach, where specialized cells called chief cells release an inactive enzyme called pepsinogen. It stays inactive until it hits the hydrochloric acid in your stomach, which drops the pH to around 1.5 to 2. At that acidity, pepsinogen clips part of itself off and becomes pepsin, the protease that starts breaking apart the proteins in your food. Signals like the hormone gastrin and low stomach pH tell chief cells to ramp up pepsinogen production.
The pancreas is the real powerhouse. Its acinar cells have the highest rate of protein synthesis of any organ in the body, churning out a suite of proteases in inactive forms: trypsinogen, chymotrypsinogen, proelastase, and procarboxypeptidase, among others. These inactive precursors travel through a duct into the small intestine, where an enzyme on the intestinal wall called enterokinase activates trypsinogen by snipping off a small fragment. The newly active trypsin then switches on all the other inactive proteases in a chain reaction. Trypsin, chymotrypsin, and elastase each cut proteins at different points along the chain, while carboxypeptidases trim amino acids from the ends.
The small intestine adds one more layer. Cells lining the intestinal wall have a “brush border” studded with peptidases, including aminopeptidases, dipeptidases, and endopeptidases. These handle the final stage of digestion, breaking small protein fragments down into individual amino acids or tiny peptides that can be absorbed into the bloodstream.
Why These Enzymes Don’t Digest You
A protease powerful enough to dissolve food proteins could easily destroy the organ that made it. The body’s solution is to manufacture proteases as zymogens, inactive precursor molecules that only become active once they reach the right location. Pepsinogen needs stomach acid. Trypsinogen needs enterokinase in the small intestine. This separation of production from activation is sometimes called the zymogen strategy, and it’s one of the most fundamental safety mechanisms in human biology.
The system isn’t perfectly binary, though. Some zymogens can spontaneously self-activate at very low levels, and some fully processed proteases stay inactive until they bind to a helper molecule. Think of it as a spectrum between “off” and “on” rather than a simple switch. When this system fails, as in acute pancreatitis, proteases activate inside the pancreas itself and begin digesting the organ, which is why pancreatitis is so painful and dangerous.
Proteases Inside Every Cell
Beyond digestion, proteases operate inside virtually every cell in your body. Lysosomes, small acidic compartments within cells, contain a family of proteases collectively known as cathepsins. These were originally thought to handle simple “bulk recycling,” breaking down old or damaged proteins. That picture has expanded considerably. Cathepsins now turn up working in the cell’s main compartment, the nucleus, and even mitochondria, performing tasks far beyond basic cleanup.
One of their most important jobs involves autophagy, the process cells use to dismantle and recycle their own worn-out components. During autophagy, a cell packages old proteins or damaged structures into a membrane-bound sac that then fuses with a lysosome. Cathepsins inside the lysosome digest the contents, freeing up raw materials the cell can reuse. When specific cathepsins are missing, undigested material piles up inside cells, disrupting normal function.
Plant Sources of Protease
Several tropical fruits are rich sources of proteases, and humans have used them for centuries, long before anyone understood enzymology.
- Papain comes from papaya fruit, roots, and leaves. It works across a wide pH range (5 to 9) and is the classic meat tenderizer. It’s also used in cheese production, beer brewing, baking, and even tooth-whitening products.
- Bromelain is extracted from pineapple stems and juice. It tolerates temperatures up to 70°C and has applications in meat processing, textile manufacturing, and medicine, where it has anti-inflammatory and blood-clot-related effects.
- Ficin comes from fig trees (specifically the latex). It’s used for meat tenderizing, milk clotting, and producing antibody fragments for medical research.
- Actinidin is found in kiwifruit. It works at lower temperatures (around 40°C) and is used commercially for breaking down chicken and fish proteins.
Beyond these four well-known enzymes, researchers have cataloged proteases in the latex of dozens of other plants, including species of Euphorbia, fig relatives, and members of the sunflower family. Many of these are serine proteases that function at alkaline pH values and show promise for dairy processing, particularly milk clotting as a vegetarian alternative to animal rennet.
Microbial and Industrial Sources
The proteases you encounter in everyday products, from laundry detergent to digestive supplements, overwhelmingly come from microbes. Bacteria in the genus Bacillus are the dominant source. Species like Bacillus amyloliquefaciens and Bacillus licheniformis produce alkaline proteases that remain active in harsh conditions, which is exactly what you need in a washing machine. Fungi in the genus Aspergillus are the other major producer. Aspergillus proteases are essential in making soy sauce, where they break down soybean protein to create the savory flavor profile.
Manufacturers grow these microbes through fermentation, often using agricultural waste as a nutrient source to keep costs down. Solid-state fermentation, where organisms grow on a moist solid substrate rather than in liquid, tends to yield high enzyme output with relatively low investment. After fermentation, the proteases are extracted using water or a mild buffer solution, then separated from the solid material by centrifugation. The liquid extract is typically freeze-dried into a stable powder. Recovery rates from this process can exceed 90%, meaning very little enzyme is lost during purification.
These microbial proteases end up in leather tanning, brewing, contact lens cleaning solutions, animal feed, and bioethanol production, in addition to the detergent and supplement markets most consumers are familiar with.
What’s in Protease Supplements
Protease supplements sold in health food stores can contain enzymes from any of these sources: animal pancreatic extracts, plant enzymes like bromelain or papain, or fungal proteases from Aspergillus. The U.S. FDA requires manufacturers to list the plant part a botanical ingredient comes from on the Supplement Facts panel. They may also list the source organism, but this is not always required in the ingredient statement if it already appears in the Supplement Facts. There is no rule requiring companies to clearly label whether a protease is animal, plant, or fungal in origin unless the source details appear in one of these two places.
If the source matters to you, whether for dietary restrictions, allergies, or preference, look at the Supplement Facts panel first. Plant-derived enzymes will typically name the fruit or plant part. Fungal sources often list the Aspergillus species. Pancreatic enzyme products usually state “pancreatin” or “pancrelipase” and may note a porcine (pig) or bovine (cow) origin. When in doubt, the manufacturer’s website or a direct inquiry to the company is often the fastest way to confirm what you’re taking.