Enteropeptidase

Enteropeptidase

Crystal structure of enteropeptidase.

Enteropeptidase, also known as enterokinase, is an enzyme crucial for the digestion of proteins in the human body. It is a serine protease that catalyzes the conversion of trypsinogen to trypsin, which in turn activates other digestive enzymes. Enteropeptidase is produced by the duodenum and plays a vital role in the digestive system.

Structure

Enteropeptidase is a complex enzyme composed of a heavy chain and a light chain. The heavy chain anchors the enzyme to the intestinal brush border, while the light chain contains the active site responsible for its enzymatic activity.

Structure of the human enteropeptidase light chain.

The light chain of enteropeptidase is a serine protease, characterized by the presence of a catalytic triad consisting of serine, histidine, and aspartate residues. This triad is essential for the enzyme's ability to cleave peptide bonds.

Function

The primary function of enteropeptidase is to initiate the activation of pancreatic zymogens. It specifically cleaves the peptide bond in trypsinogen, converting it into active trypsin. Trypsin then activates other zymogens, such as chymotrypsinogen, proelastase, and procarboxypeptidase, facilitating the digestion of proteins into amino acids.

Mechanism of Action

Enteropeptidase recognizes a specific sequence of amino acids in trypsinogen, known as the activation peptide. The enzyme cleaves the peptide bond at the carboxyl side of a lysine residue, resulting in the formation of active trypsin. This process is highly specific and ensures that trypsin is activated only in the small intestine, preventing premature activation of digestive enzymes in the pancreas.

Clinical Significance

Deficiency or malfunction of enteropeptidase can lead to severe digestive disorders. A lack of enteropeptidase activity results in the inability to activate trypsinogen, leading to protein malabsorption and malnutrition. Genetic mutations affecting enteropeptidase can cause congenital enteropeptidase deficiency, a rare condition characterized by diarrhea, failure to thrive, and hypoproteinemia.

Related Pages

• Trypsin
• Chymotrypsin
• Digestive enzyme
• Serine protease