Understand that the different proteases present in the stomach and the duodenum work best at different pH levels

SouravNovember 2, 2024

Answered step-by-step

Different proteases present in the stomach and duodenum function optimally at different pH levels, which is crucial for effective protein digestion. Here’s a detailed description of how this works:

1. Stomach Proteases

Pepsin

• Optimal pH: Pepsin, the primary protease in the stomach, functions best at a highly acidic pH of approximately 1.5 to 2.
• Function: Pepsin is secreted as an inactive precursor called pepsinogen by gastric chief cells. Hydrochloric acid (HCl) in the stomach activates pepsinogen to pepsin when it enters the acidic environment.
• Role in Digestion: At this low pH, pepsin effectively breaks down proteins into smaller peptides, facilitating further digestion as the food moves into the small intestine.

2. Duodenal Proteases

Trypsin and Other Alkaline Proteases

• Optimal pH: In contrast to pepsin, proteases such as trypsin, which are active in the duodenum, function optimally at a more alkaline pH of around 7.5 to 8.5.
• Function: Trypsin is produced in the pancreas as trypsinogen (an inactive form) and is activated in the small intestine by the enzyme enteropeptidase. Other proteases produced by the pancreas include chymotrypsin and carboxypeptidase, which also operate effectively in alkaline conditions.
• Role in Digestion: These alkaline proteases continue the process of protein digestion initiated by pepsin, breaking down peptides into smaller amino acids that can be absorbed by the intestinal lining.

Summary of pH Dependence

• Stomach (Pepsin):
  • Optimal pH: 1.5 – 2
  • Active Enzyme: Pepsin
  • Substrate: Proteins
  • End Products: Smaller peptides
• Duodenum (Trypsin and Others):
  • Optimal pH: 7.5 – 8.5
  • Active Enzymes: Trypsin, chymotrypsin, carboxypeptidase
  • Substrate: Peptides
  • End Products: Amino acids