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

Intestinal disaccharide uptake was studied with isolated brush-border membrane vesicles lacking the corresponding hydrolase. Either 15-day-old chick intestine, lacking both trehalase and lactase, or newborn pig intestine, lacking sucrase, was used. Both animal species yielded osmotically active vesicles capable of D-glucose/Na+ cotransport with a positive overshoot test. Vesicles from either origin gave quantitatively similar results in regard to both initial uptake rates and relative vesicle volumes. The nontransported analogs D-mannitol and L-glucose were used as diffusion markers. When tested with the appropriate disaccharidase-lacking vesicles, lactose, trehalose and sucrose exhibited uptake rates indistinguishable from those of D-mannitol and L-glucose. These uptakes were unaffected by the presence or absence of Na+, phlorizin and Tris. Chromatographic analysis confirmed the lack of hydrolysis of each disaccharide after prolonged incubation. The inescapable conclusion seems to be that intact disaccharides are not transported through the brush-border membrane, their uptake occurring through simple diffusion.
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PMID:Disaccharide uptake by brush-border membrane vesicles lacking the corresponding hydrolases. 643 45

Lactose absorption capacity was determined by lactose tolerance tests with breath hydrogen determination in 102 healthy, adult, Hungarian pairs of twins in order to test monogenic Mendelian inheritance of the absorptive lactase phenotypes, lactose absorber and lactose malabsorber. Of the total, 52 pairs were monozygous (MZ) and 50 dizygous (DZ) twins of identical sex. All MZ twins were concordant with respect to lactase phenotype. Among DZ twins, the distribution of lactase phenotypes was in agreement with Hardy-Weinberg expectations derived from the frequencies of the hypolactasia gene in DZ and MZ twins, and in the general Budapest population. In the second part of the study, three commonly used methods of lactose tolerance testing, the blood glucose, the blood galactose, and the breath hydrogen tests, were compared in 49 pairs of twins concordant for lactase phenotype. Blood galactose concentration showed the greatest and only significant difference between the intrapair correlation coefficients of MZ and DZ, and no overlap between lactose absorbers and lactose malabsorbers. The intrapair correlation coefficients of peak breath hydrogen concentration in MZ and DZ twins did not significantly differ from zero, but the resolution of lactase phenotypes was satisfactory. Differences in glucose absorption and concentration in lactose absorbers and malobsorbers overlapped considerably, and among lactose absorbers correlation coefficients in DZ were higher than in MZ twins. In MZ and DZ twins, the difference in concordance and constancy of lactose intolerance symptoms was not significant.
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PMID:A study of lactose absorption capacity in twins. 643 76

To test the hypothesis that in subjects with low intestinal lactase activity (LLA) lactose solutions leaves the stomach at an abnormally fast rate, we have measured the gastric emptying rate of solutions of lactose and glucose-galactose in patients with LLA (n = 9) and in control subjects with high intestinal lactase levels (n = 7) as proved by the assay of disaccharidases in specimens of intestinal mucosa. The volume of the test meals was 300 ml. Lactose solutions contain 50 g of disaccharide and glucose-galactose solutions contain 25 g of each monosaccharide. The volumes remaining in the stomach at different times after the intragastric instillation of the test meals were estimated by the double sampling test meal. In the control group, minor differences between lactose and glucose-galactose gastric emptying rates was found. By contrast, in LLA patients, the lactose meal left the stomach at a significantly faster rate than the glucose-galactose test meal. These findings support previous evidence obtained in patients with putatively low intestinal lactase activity and are consistent with the view that duodenal osmoreceptors, whose excitation results in inhibition of gastric emptying, lie deeper than the disaccharidases in intestinal mucosa. Thus, incomplete hydrolysis of lactose results in a faster than normal gastric emptying rate of the sugar and this may contribute to the symptoms found in LLA patients after milk ingestion.
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PMID:Gastric emptying of lactose and glucose-galactose in patients with low intestinal lactase activity. 662 55

Two experimental models to examine the relationship between host nutrition and parasitic infection are considered. Moniliformis dubius, an acanthocephalan parasite of the laboratory rat, is dependent on the type and amount of host dietary carbohydrate for growth and reproduction. Starch, glucose, fructose, and mannose in host diets support parasite growth and development, but much lower dietary amounts of starch, fructose, and mannose are needed compared to free glucose. The pig-Ascaris suum relationship is considered as a model for human ascariasis. Experimental Ascaris infections in pigs resulted in reduced growth, reduced food intake, lowered biological value of dietary protein, and reduced intestinal lactase activity and lactose tolerance. These results are similar in some respects to reported effects of Ascaris infection in humans.
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PMID:Some experimental approaches to the study of nutrition and parasitic infection. 669 43

We studied the uptake of D-glucose and L-tryptophan by the small intestine and estimated the activities of the intestinal brush border enzymes (sucrase, lactase, NA+-K+-ATPase and alkaline phosphatase) and lysosomal enzymes in rats receiving T-2 toxin orally. considerable decrease occurred in glucose and tryptophan uptake and in brush border sucrase, lactase and (Na+-K+)-ATPase. Alkaline phosphatase activity and release of lysosomal enzymes (acid phosphatase and acid ribonuclease) was unchanged.
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PMID:Effects of T-2 toxin on glucose and tryptophan uptake and intestinal mucosal enzymes. 671 77

The effect of folate deficiency, induced by a folate deficient diet, on the digestive and absorptive functions of the intestinal epithelium in rats has been investigated. The intestinal uptake of D-glucose and L-alanine and the brush border sucrase, lactase and alkaline phosphatase activities were considerably depressed in folate deficient animals compared to the control group. Kinetic studies with brush border sucrase in control and deficient animals revealed that reduced levels of the enzyme in folate deficiency are due to a reduced number of enzyme molecules. There was no change in activity of lactate-dehydrogenase in enterocytes of folate deficient rats.
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PMID:Effect of folate deficiency on the digestive and absorptive functions of intestinal epithelium in rats. 679 38

Regulation of lactose (beta-D-galactosidase) synthesis in the lactose-utilizing yeast Candida pseudotropicalis was studied. The enzyme was inducible by lactose and galactose. When grown on these sugars the enzyme level of the yeast was 20 times or higher than when grown on glycerol. The Km and optimal pH were similar for the lactase induced either by lactose or galactose. The hydrolysis of o-nitrophenyl-beta-D-galactopyranoside by the lactase was inhibited by galactose and several analogs and galactosides, but not by glucose. Lactose uptake activity observed in lactose-grown cells was very reduced in cells grown on glucose or galactose. Glucose repressed the induction of lactase, but not the metabolic system for galactose utilization. In continuous culture on lactose medium at dilution rates below 0.2 h-1 the specific lactase activity was higher than in batch cultures and decreased with increases in dilution rate. Lactase was induced by pulses of lactose and galactose in cells growing on glucose, but only at low dilution rates were the steady-state concentration of glucose was very low.
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PMID:Regulation of beta-D-galactosidase synthesis in Candida pseudotropicalis. 680 Mar 4

Examined in this article is presently available evidence for the hypothesis that some types of senile cataracts may be brought on by decades-long consumption of milk and milk products. The author approaches the question from a background of research in the geography and history of dairying as these relate to present-day differences among the world's peoples in prevalence of primary adult lactose malabsorption, which is based on a deficiency of the enzyme lactase in adulthood. Among peoples who have consumed milk in lactose-rich forms over a long historical period, there seems to have been a mutation for persistence of high lactase activity throughout life (PHLA), which distinguishes them from human populations of nonmilking tradition and from most land mammals. PHLA permits greater intestinal hydrolysis of lactose and absorption of galactose by adults. The mutation for PHLA, however, was not accompanied by a second one raising galactokinase activity to high levels through life. The result may be that adults who consume large quantities of milk, who have high lactase activity, lactose hydrolysis, and galactose absorption, suffer repeated small galactose challenges, accumulation of galactitol in the lens, and a greater likelihood of developing senile cataracts.
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PMID:A geographic approach to senile cataracts: possible links with milk consumption, lactase activity, and galactose metabolism. 680 98

Nutritional balances are made with groups of 12 rats Wistar receiving well-balanced diets with 40 p. 100 of sucrose (T), or 40 p. 100 of lactose (L and P), or hydrolyzed lactose (LH and PH). Whey (L) and ultrafiltration permeate (P) are used in crude state or after enzymic industrial lactase hydrolysis (LH and PH). The animals consume diets during eight months. Faeces contain neither lactose nor galactose, but glucose in small quantities. In all urines occurs about 0,5 mg/day of glucose. The lactose diets (L and P) provoke a week lactosury (0,36 p. 100 of ingestion). Galactose and galactitol are abundant in urines: with lactose diets (L and P), the urinary excretion is equal to 4 p. 100 of ingested galactose. In urines of hydrolyzed lactose diets (LH and PH) the excretion reaches 26 p. 100 of ingestion. In this case the excretion is remarkably invariable from third day of eighth month: the urinary galactose corresponds to 23 p. 100 and galactitol to 3 p. 100 of consumed galactose. The urines of lactose diets (L and P) and hydrolyzed lactose diets (LH and PH) contain 100 and 300 mg/day of non sugar reducing substances respectively, i.e. 40 p. 100 of total urinary reducing power. The apparent retention of lactose (L and P) is 95,5 p. 100 and that of the hydrolyzed lactose (LH and PH) is 86 p. 100 after 8 months of experiment but it is estimated that digestive flora consumes 40 p. 100 of dietary lactose (L and P).
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PMID:[Effect of prolonged consumption of lactose or hydrolyzed lactose in the rat. 2. Digestibility, retention and utilization of lactose components]. 708 7

Imposition of undernutrition during the suckling period considerably enhanced the intestinal uptake of D-glucose and glycine compared to a control group. Brush border sucrase, and alkaline phosphatase activities were drastically reduced while lactase and leucine amino peptidase levels were significantly elevated at weaning in nutritionally deprived pups as compared to control animals. Cortisone administration to undernourished rats depressed the uptake of D-glucose but stimulated that of glycine. Thyroxine treatment to undernourished animals reduced the uptake of glucose but had no effect on glycine absorption. Brush border sucrase and alkaline phosphatase activities were stimulated in cortisone- or thyroxine-injected undernourished rats but lactase activity was depressed under these conditions. Leucine aminopeptidase activity remained unaffected in cortisone- or thyroxine-administered undernourished pups.
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PMID:Alterations in intestinal function in response to thyroxine and cortisone administration in undernourished rats. 713 57


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