Enterokinase is an enzyme that plays a fundamental role in the human digestive system. It functions as a catalyst, speeding up biochemical reactions without being consumed. This enzyme is a key component in breaking down proteins into smaller, absorbable units.
Where Enterokinase is Found
Enterokinase, also known as enteropeptidase, is found in the lining of the duodenum, the first segment of the small intestine after the stomach. Specialized cells in the duodenal mucosa produce and secrete this enzyme. Once produced, enterokinase is secreted onto the brush border, a specialized surface of intestinal cells rich in digestive enzymes. It is classified as a serine protease, an enzyme that cleaves peptide bonds in proteins.
How Enterokinase Works
Enterokinase converts an inactive enzyme precursor into its active form. Its target is trypsinogen, an inactive enzyme (zymogen) produced by the pancreas. Enterokinase cleaves a peptide bond within the trypsinogen molecule, transforming it into its active counterpart, trypsin. This conversion is a crucial initial step in protein digestion within the small intestine. Enterokinase is unique because it is the only enzyme known to initiate this activation of trypsinogen.
The Digestive Activation Chain
The activation of trypsin by enterokinase initiates a cascade of further enzymatic activations, essential for comprehensive protein digestion. Once active, trypsin activates other inactive digestive enzymes secreted by the pancreas. These include the conversion of chymotrypsinogen into chymotrypsin, procarboxypeptidases into carboxypeptidases, and proelastase into elastase. This chain reaction ensures a full complement of protein-digesting enzymes becomes available in the small intestine. Enterokinase acts as a master switch, making it indispensable for efficient protein breakdown and nutrient absorption.
When Enterokinase Doesn’t Work Properly
Dysfunction or absence of enterokinase can have health consequences due to its role in activating digestive enzymes. Genetic mutations can lead to a rare condition called congenital enterokinase deficiency. In individuals with this condition, enterokinase is either completely absent or its function is severely impaired. This impairment results in an inability to properly digest proteins, leading to protein malabsorption.
Symptoms include chronic diarrhea, failure to thrive in infants, and edema, which is swelling caused by fluid retention due to low protein levels. Diagnosis involves enzyme assays, and treatment includes administering pancreatic enzyme supplements to aid digestion.