After proteases finish digesting food in the duodenum, they move with chyme into the mid and distal small intestine and begin digesting themselves and other enzymes into amino acids.

Verified by Lenz · May 30, 2026

The Short Version

The evidence supports that pancreatic proteases continue moving with chyme beyond the duodenum and may be degraded during transit. But the claim misstates both timing and mechanism: protein digestion is not simply finished in the duodenum, and free amino acids are produced mainly through brush-border and intracellular peptidases, not primarily by proteases digesting themselves and other enzymes.

Caveats

The wording falsely suggests digestion is completed in the duodenum before enzymes move onward; in reality, digestion continues through the small intestine.
Some enzyme degradation in the lumen does occur, but that does not mean pancreatic proteases are the main source of converting those proteins all the way into free amino acids.
Several lower-quality or commercial sources generalize proteolysis too broadly; higher-authority physiology references give a different and more specific mechanism.

The Receipts

The Influence of Peptidases in Intestinal Brush Border Membranes on Bioactive Peptide Generation
PubMed CentralOct 13, 2020
Fate of pancreatic enzymes in the human intestinal lumen in pancreatic insufficiency
PubMedJan 1, 1994
Physiology, Digestion - StatPearls
NCBI BookshelfMar 20, 2023
Non-Pancreatic Digestive Enzymes
PubMed Central
Feedback regulation of human pancreatic secretion. Effects of different levels of intraluminal proteases on duodenal delivery and intraluminal fate of enzymes
PubMedJan 1, 1990
Trypsin
BritannicaJan 10, 2024
Biochemistry, Digestion and Absorption
NCBI BookshelfMar 5, 2024
Protein Digestion Mechanism - Mtoz Biolabs
MtoZ BiolabsSep 27, 2023
Intestinal Proteases
NIH / PMCNov 10, 2023
Human Intestinal Brush Border Peptidases
GastroenterologyFeb 1, 1985

+ 24 more sources — see the full list on Lenz

Filed Under

Amino AcidsChymeDuodenumProteaseSmall Intestine

After proteases finish digesting food in the duodenum, they move with chyme into the mid and distal small intestine and begin digesting themselves and other enzymes into amino acids.

The Short Version

Caveats

The Receipts

Filed Under

More Fact Checks

Pancreatic proteases such as trypsinogen and chymotrypsinogen are synthesized as inactive zymogens and are activated in the duodenum by an intestinal enzyme (enterokinase/enteropeptidase), which helps prevent autodigestion of the pancreas.

Most digestive enzymes produced by the small-intestinal wall are bound to the apical (brush-border) cell membrane of intestinal epithelial cells rather than being freely secreted into the intestinal lumen.

Under normal conditions, only a very small fraction of dietary amino acids in the small-intestinal lumen are diverted by other substances or are consumed by colonic bacteria before being absorbed, so amino-acid loss is very low.