Hypolactasia as a molecular basis of lactose intolerance.
Lactase-phlorizin hydrolase (LPH), a membrane-bound glycoprotein present in the luminal surface of enterocytes in the intestine is responsible for lactose intolerance, a phenomenon prevalent in humans worldwide. In the rodent intestine, the post-natal development of the LPH follows a specific pattern, such that the enzyme levels are high in the peri-natal period, but declines considerably upon maturation. The observed maturational decline in the LPH activity is very similar to adult-type hypolactasia observed in humans. Majority of the studies have been carried out using animal models or cell lines and a number of hypotheses have been put forward to explain the maturational decline of lactase activity such as: (a) decreased amount of lactase protein, (b) defect in post-translational modification of precursor lactase to the mature enzyme, and (c) synthesis of an inactive, high molecular weight lactase with altered glycosylation, however, the precise underlying mechanism of adult-type hypolactasia remains undefined. The present review describes the recent developments in understanding the regulation of lactase expression and the possible mechanism of adult-type hypolactasia, as a cause of lactose intolerance.
Kaur
Kamaljit
K
Department of Biochemistry, Panjab University, Chandigarh 160 014, India.
Mahmood
Safrun
S
Mahmood
Akhtar
A
D000818:Animals; D015971:Gene Expression Regulation, Enzymologic; D006031:Glycosylation; D006801:Humans; D043322:Lactase / Q000096:biosynthesis; D010694:Lactase-Phlorizin Hydrolase / Q000737:chemistry; D007785:Lactose / Q000235:genetics / Q000378:metabolism*; D007787:Lactose Intolerance / Q000209:etiology*; D011110:Polymorphism, Genetic
D043322:Lactase; D010694:Lactase-Phlorizin Hydrolase; D007785:Lactose