title: Gene-dosage effect on intestinal lactase activity demonstrated in vivo.
abstract: The activities of the disaccharidases lactase, maltase, and sucrase were determined in upper jejunal biopsies of 65 healthy adult German males. The study was an attempt to demonstrate the gene-dosage effect on lactase activity expected from the presence of a "hypolactasia" (l) and a "lactase-persistence" (L) allele in the German population. In contrast to lactase/sucrase ratios, lactose/maltose ratios showed a trimodal distribution in proportions of presumed genotypes LL, Ll, and ll compatible with Hardy-Weinberg equilibrium. The frequency of homozygotes ll (13.8%) was similar to the average frequency of lactose malabsorbers in Germany reported in the literature. The importance of considering the lactase gene-dosage effect in population studies of lactase activity is discussed.
mesh_terms: D000328:Adult; D000483:Alleles; D004186:Disaccharidases / Q000235:genetics; D004303:Dosage Compensation, Genetic; D005696:Galactosidases / Q000235:genetics*; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D007583:Jejunum / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D013393:Sucrase / Q000235:genetics; D000520:alpha-Glucosidases / Q000235:genetics; D001616:beta-Galactosidase / Q000235:genetics*
chemical_list: D004186:Disaccharidases; D005696:Galactosidases; D000520:alpha-Glucosidases; D001616:beta-Galactosidase; D013393:Sucrase