What causes trehalase deficiency?

There are many disaccharidases in the small intestinal mucosa of normal people, such as lactase, which can decompose lactose into galactose and glucose; maltase, which can decompose maltose into glucose and isomaltose; isomaltase, which can decompose isomaltose into two molecules of glucose; sucrase, which can decompose sucrose into glucose and fructose; and trehalase, which can decompose trehalose into two molecules of glucose. For some reason, the lack of disaccharidases causes the digestion and absorption of disaccharides to be impaired, leading to diarrhea. This disease is not uncommon in clinical practice, but it is often not taken seriously.

Infants may have sucrase and isomaltase deficiencies due to genetic factors. The defect of sucrose-isomaltose malabsorption is mainly in sucrose, while the isomaltase defect is secondary. Studies have shown that the enzyme is defectively processed in the cell and accumulates in the endoplasmic reticulum. The enzyme complex is blocked in the Golgi complex, while the altered enzyme is transported to the cell surface. Due to the above factors, this single gene disease can be heterogeneous. The enzyme gene is located on chromosome 3q and is an autosomal recessive genetic disease. Homozygotes have symptoms throughout life, while heterozygotes only have symptoms in infancy and the symptoms can disappear in adulthood. Giving fresh yeast or live yeast can alleviate its symptoms.

The gene of human lactase phlorizin hydrolase is located on chromosome 2. When the brush border of the small intestinal mucosa of infants lacks lactase, watery diarrhea will occur after the first breastfeeding.

The most common disaccharidase deficiency in adults is lactase deficiency. Lactase activity is highest in newborns and can be reduced to 10% of its maximum amount later. Adults with lactase deficiency are at this level. After infants are weaned, lactase gradually decreases, and diarrhea is easily caused when they take milk again. The deficiency of this enzyme is related to genetics, accounting for 5% to 30% in Caucasians and 75% in people of color, including Asians and Africans. Sucrose-isomaltase deficiency can be reduced to 10% to 20% of normal, and the intestinal mucosa is normal. The reason is still unknown. In addition, during gastrointestinal infections, disaccharidase can also be temporarily under-secreted.