BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 6. AMINO ACID METABOLISM AND FUNCTIONS. PROTEIN BIOSYNTHESIS

6.3. Protein Digestion

6.3.5. Disorders of Protein Digestion and Amino Acid Transport

A small fraction of Protein Digestion products consists of unhydrolyzed short Peptides. Some individuals develop an Immune Response to dietary protein ingestion, which is apparently related to the absorption capacity for such peptides. Products of fully digested Proteins (Amino Acids) lack antigenic properties and do not trigger immune reactions.

In newborns, the permeability of the intestinal mucosa is higher than in adults, allowing colostrum Antibodies (a secretion of the Mammary Glands produced in the first days after birth, enriched with antibodies and antitoxins) to enter the bloodstream. This process is enhanced by a Trypsin inhibitor protein present in colostrum. Proteolytic Enzymes in the digestive secretions of newborns have low activity. These mechanisms facilitate the intestinal absorption of small amounts of native proteins sufficient to induce an immune response.

Increasing evidence Supports the hypothesis that celiac disease (nontropical sprue) involves impaired functional activity of intestinal mucosal Cells responsible for absorbing small, unhydrolyzed peptides. Celiac disease is characterized by hypersensitivity to gluten, a storage protein found in cereal grains consumed by humans. This protein exerts a toxic effect on the small intestinal mucosa, leading to pathological changes and malabsorption. The Pathogenesis of the disease remains insufficiently understood.

Conditions such as cystinuria, Hartnup disease, and several others arise from defects in neutral amino acid transporters in the intestine and Kidneys. A congenital pathology associated with a deficiency of the enzyme 5-oxoprolinase has also been described (Fig. 6.5, reaction 4). In this condition, oxoproline is excreted in the urine. Such patients experience impaired Amino Acid Transport into Tissues and abnormal cellular METABOLISM.



Last update: 06/08/2026

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