Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A limited fraction of the human adult population retains intestinal lactase-phlorizin hydrolase (LPH) activity during adulthood, and this is called the lactase persistence phenotype. However, 95% of all adults have adult-type hypolactasia (ATH) and have difficulty digesting milk sugar. Rarely, some infants are born with an inability to digest lactase (congenital lactase deficiency or CLD) due to low levels of LPH activity, which results in severe clinical consequences if not properly diagnosed and treated by lactose avoidance. Recently, it has been shown that both recessive LPH deficiencies, CLD and ATH, are related to DNA variants affecting the lactase (LCT) gene, but they are mediated through very different molecular mechanisms. The LCT mutations resulting in childhood CLD lead to low LPH activity through nonsense-mediated LCT mRNA decay, whereas the critical nucleotide variants for the ATH phenotype represent distal enhancer polymorphisms, which regulate developmentally LCT transcript levels in intestinal cells.
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PMID:Molecular differentiation of congenital lactase deficiency from adult-type hypolactasia. 1734 62

Intestinal lactase is required for the hydrolysis of lactose that is the most essential carbohydrate in milk and the primary diet source of newborn. Congenital lactase deficiency [CLD (MIM 223000)] is a severe gastrointestinal disorder and is characterized by watery diarrhea due to an extremely low or the lack of lactase activity in the intestinal wall from birth. CLD is a rare disease and occurs more frequently in Finland. Recent studies have shown that mutations in the coding region of the lactase (LCT) gene underlie CLD in patients from Finland and other European countries. Here, we report two novel mutations in the LCT gene in a Japanese female infant with clinical features consistent with those of CLD. She suffered from severe watery diarrhea from the age of 2 days on breast milk/lactose containing cow's milk formula. With the lactose-free hydrolyzed cow's milk formula, diarrhea was stopped, and she has now developed well on a lactose-free diet. She shows a lactose-intolerance pattern on the lactose challenge test. Sequence analysis revealed the two mutations in her LCT gene: c.4419C>G (p.Y1473X) in exon 10 transmitted from her mother and c.5387delA (p.D1796fs) in exon 16 transmitted from her father. Both mutations cause premature truncation of lactase polypeptide and are supposed to be responsible for CLD. To our knowledge, this is the first report on mutations in the LCT gene in Japan. We suggest that an increased awareness is required regarding CLD.
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PMID:Two novel mutations in the lactase gene in a Japanese infant with congenital lactase deficiency. 2268 20