د.نبيل صبرى النطاح2026-11-012026-11-01https://dspace.academy.edu.ly/handle/123456789/2704The direct method is an invasive method in which intestinal biopsy specimen processed for an assay of mucosal disaccharides according to the standard method developed mainly by Dahlqvist and Burgess (Dahlqvist, 1964). Diagnosis of hypolactasia is suggested when the lactase activity< 20 IU/g protein and lactase/sucrase ratio <0.03 with normal histology.The milk sugar lactose (the main carbohydrate in mammalian milk) is hydrolysing to glucose and galactose in the intestinal epithelial cells by Lactase-phlorizin hydrolase enzyme (LPH) (EC 3.2.1.23/62). LPH is an integral glycoprotein of the microvillus membrane of small intestinal epithelial cells(Mantei et al., 1988). The mature enzyme has two catalytic enzymatic activities: Lactase (-d-Galactoside galactohydrolase) (EC 3.2.1. 23) responsible for hydrolysing lactose to glucose and galactose, and the phlorizin hydrolase (glycosyl-N-acyl-sphinocsine glucohydrolase)(EC .3.2.1 62) responsible for hydrolysing aryl and alkyl - glycosides to phlorizin and -glycosylceramides (which are part of diet of most vertebrates) (Lorenz-Meyer et al., 1972; Schlegel-Haueter et al., 1972; Colombo et al., 1973; Skovbjerg et al., 1981; Skovbjerg et al., 1982; Keller P, 1993; Arola, 1994; Enattah, 2005).Study of genetic variants of Lactose