Definition of pepsin in English:

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Pronunciation: /ˈpɛpsɪn/


[mass noun] Biochemistry
The chief digestive enzyme in the stomach, which breaks down proteins into polypeptides.
Example sentences
  • Proteins in the stomach are broken down to polypeptides by the enzyme pepsin, which works best in acidic environments and is produced by ‘chief’, or ‘zymogen’, cells in the gastric mucosa.
  • Such damage results from the low pH of stomach acids working in conjunction with the digestive enzyme pepsin.
  • Many people take extra doses of naturally produced enzymes, such as lactase, pepsin and trypsin, in supplement form.


Mid 19th century: from Greek pepsis 'digestion' + -in1.

For editors and proofreaders

Line breaks: pep¦sin

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