title: The effect of the digestion products of lactose (glucose and galactose) on its intraintestinal, in vivo hydrolysis by exogenous microbial beta-D-galactosidase.
abstract: Exogenous, microbial beta-D-galactosidases are capable of effecting hydrolysis of lactose in situ in the gastrointestinal tract of lactase-deficient subjects when given as replacement therapy at mealtime. As its digestion products-glucose and galactose-are known to inhibit lactose hydrolysis in vitro, the effect of adding excess monosaccharide to milk on the hydrolytic efficiency of a beta-galactosidase from Aspergillus niger in adult lactose-malabsorbers was tested. Subjects were studied with 360-ml volumes of milk containing 18 g of carbohydrate. This was administered as intact milk, as lactose-prehydrolyzed milk, and as milk to which 399 mg of Lactase N was added within 5 minutes of consumption. This latter Lactase N-treated milk was administered alone and with graded levels of glucose-9, 18, and 36 g-and with similar doses of galactose. The Lactase N enzyme alone at mealtime reduced breath H2 production by 68% as compared to intact milk. The addition of monosaccharides produced no change in the apparent hydrolytic efficiency of the Lactase N in situ. Thus, product inhibition is unlikely to be the basis for the limited efficiency of intraintestinal hydrolysis of milk lactose by the enzyme from A niger.
mesh_terms: D000328:Adult; D000818:Animals; D001234:Aspergillus niger / Q000201:enzymology; D001944:Breath Tests; D005260:Female; D005690:Galactose / Q000494:pharmacology*; D005696:Galactosidases / Q000378:metabolism*; D005769:Gastrointestinal Motility / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D006868:Hydrolysis; D007413:Intestinal Mucosa / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism; D007787:Lactose Intolerance / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008892:Milk; D001616:beta-Galactosidase / Q000008:administration & dosage / Q000378:metabolism* / Q000627:therapeutic use
chemical_list: D006859:Hydrogen; D005696:Galactosidases; D001616:beta-Galactosidase; D005947:Glucose; D007785:Lactose; D005690:Galactose