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

The effect of oral intake and body weight on postnatal maturation of the small intestine was examined in infant rabbits with accelerated weight gain. Intestine from immature animals is characterized by large unidirectional Na fluxes, failure of Na absorption to respond to glucose but increased ability to absorb monosaccharides, and an enzyme pattern of high lactase and thymidine kinase and low sucrase. Postnatal development was monitored by measuring Na and glucose transport in short-circuited jejunum and enzyme activities in jejunal mucosa. Accelerated weight gain was achieved in the experimental group by reducing litter size to 3 animals at 24-48 hours of age. Under glucose-free conditions unidirectional Na fluxes were significantly smaller in tissue from the heavier experimental animals compared to controls. The addition of glucose had no effect on Na fluxes in control tissue but significantly increased Na absorption in the experimental group. Unidirectional and net fluxes of 14C-D-glucose were significantly smaller in the heavy experimental animals compared to controls. Isolated villus enterocytes from the experimental group had reduced lactase and thymidine kinase activities. Sucrase activity, which did not differ in isolated cells, was increased in total mucosa from the experimental group. Solute transport and the enzyme profile in jejunum from the heavier experimental suckling rabbits is characteristic of intestinal epithelium from more mature animals, indicating accelerated postnatal maturation. The findings suggest that oral nutrient intake and body weight, rather than chronologic age, act as the physiologic trigger for postnatal maturation of the small intestine.
 ...
PMID:Effect of body weight on postnatal development of the proximal small intestine of the rabbit. 713 89

In acute diarrhea of infancy we distinguish between infectious and noninfectious causes. In the latter we know some autosomal recessive disorders, e.g. the glucose-galactose-malabsorption, the lactase deficiency as well as the sucrase-isomaltase deficiency. In addition the most frequent acquired disorders like the cow's milk protein intolerance and celiac disease contribute also to the group of noninfectious causes of diarrhea. Here the most effective therapy consists of the elimination of the toxic agent from the diet. In infectious diarrhea we find most frequently rotavirus as the agent but also yersinia, campylobacter fetus, salmonella, shigella, E. coli, lamblia giardia and entameba hystolytica. Generally a conservative treatment with a dietetic regimen is preferred. Only in severe cases with yersinia and campylobacter infection the addition of antibiotic drugs is necessary. Giardia lamblia and amebiasis however have to be treated with metronidazol. As the absorption of glucose is coupled with that of sodium within the small intestine in acute gastroenteritis we find a combined disturbance between salt and carbohydrate absorption. A solution containing glucose and salt is recommended therefore for oral rehydration. The amount administered within the first 24 hours should be between 150-250 ml/kg per day. So called "antidiarrhoic drugs" are questionably effective.
 ...
PMID:[Useful and superfluous measures in the treatment of infant diarrhea]. 717 37

It is well established that Giardia infection causes malabsorption. However, the precise mechanism of such a malabsorption is not known. To investigate this, transport studies, using the tissue accumulation technique, were carried out in mice infected with G. lamblia obtained from human stools. There was a significant fall in the transport of D-glucose, L-alanine and glycine in the infected animals compared with the controls. Kinetics of the D-glucose and glycine transport system were examined by measuring the tissue uptake in the presence of different concentrations of the substrate. For glucose, the affinity constant (Km) for the transport site was the same (4 . 37mM) in normal and infected animals but the maximal transport rate (V max) was considerably reduced in infected animals (158 . 7 mu moles/hr/g tissue) compared with (357 . 1 microgram moles/hr/g tissue) in controls. Results with glycine were similar; the Km was similar in control and infected animals (5 . 7 mM) whereas the V max was reduced in infected animals (27 . 02 microgram moles/hr/g tissue) compared with controls (45 . 5 micrograms moles/hr/g tissue). Analysis of the intestinal enzymes showed a significant decrease in the levels of brush border sucrase, lactase and alkaline phosphatase in infected animals; the cellular enzymes, LDH, GOT and GPT remained unaffected. The observed aberrations in the transport functions and brush border enzymes suggest that G. lamblia causes malabsorption by damaging the epithelial membrane of the enterocyte.
 ...
PMID:Transport studies and enzyme assays in mice infected with human Giardia lamblia. 717 14

The effect of undernutrition during suckling has been investigated on the brush border enzymes and the intestinal uptake of D-glucose and glycine in rats at weaning. The brush border sucrase and alkaline phosphatase activities were drastically reduced, but lactase and leucine aminopeptidase levels were significantly elevated in the intestine of nutritionally deprived pups compared to controls. The uptake of D-glucose and glycine in undernourished rats was also augmented. The chemical composition of the brush border membrane analyzed in nutritionally deficient animals revealed an enhancement of the membrane protein, sialic acid, cholesterol, and phospholipids compared to the control group. [U-14C]D-Glucose incorporation into lipid constituents of the membrane suggested that the observed enhancement of the membrane lipids is the result of an increased synthesis in response to undernutrition.
 ...
PMID:Intestinal brush border membrane structure and function: effect of early postnatal undernutrition. 725 34

The in vitro and in vivo production of hydrogen gas (H2) from various carbohydrates or proteins has been examined in normal rats and in rats infected with the nematode Nippostrongylus brasiliensis. Normal rat fecal homogenates were capable of producing H2 in vitro from glucose, sucrose, xylose, lactulose, bovine serum albumin, or casein hydrolysate. Direct injection of glucose, sucrose, xylose, lactulose, bovine serum albumin, or casein hydrolysate into the cecum of normal rats resulted in approximately twice as much H2 production in vivo than when these same carbohydrates or proteins were administered to the normal rats by gavage. Partial small intestinal villous atrophy was produced by infecting rats with the nematode N. brasiliensis. Impaired small intestinal cell function and evidence of malabsorption in the nematode-infected rats included: (a) decreased activity of intestinal cell lactase (-43%), sucrase (-33%), and alkaline phosphatase (-46%); (b) decreased gut sac uptake of 3-O-(methyl-3H]-D-glucose (-21%) or 1-[carboxyl-14C]-aminocyclopentane-1-carboxylic acid (-28%); and (c) increased (+ 64%-561%) 14CO2 production after D-[U-14C]xylose administration. These rats produced approximately twice as much H2 after gavage administration of glucose, sucrose, xylose, bovine serum albumin, or casein hydrolysate compared with normal rats. The present study suggests that H2 analysis may be useful in the evaluation of small intestinal malabsorption states in rats.
 ...
PMID:Use of hydrogen gas (H2) analysis to assess intestinal absorption. Studies in normal rats and in rats infected with the nematode, Nippostrongylus brasiliensis. 728 87

Lactose malabsorption can be demonstrated by detecting hydrogen (H2) in the expired air after oral loading with lactose. A comparative study was carried out on 24 subjects. Following an oral loading dose of lactose, the H2 eliminated during expiration was assayed by gas chromatography, and blood galactose levels were measured. The results showed that the test was reliable, well tolerated and reproductible. However, the method does not measure the amounts of lactase present in the intestinal mucosa. The lactose loading test seems to be valuable for studies on lactose and carbohydrate malabsorption.
 ...
PMID:[Lactase deficiency in the intestinal mucosa. Demonstration by hydrogen detection in the expired air after lactose loading (author's transl)]. 744 88

Human lactase-phlorizin hydrolase [EC 3.2.1.23-3.2.1.62] is a disaccharidase located in the microvillus membrane of small intestinal epithelial cells. The enzyme is synthesized as a precursor protein in the endoplasmic reticulum and in addition to being glycosylated is subsequently proteolytically processed to the mature microvillus membrane-bound form after passing the trans-Golgi compartment. We studied the oligomerization of human lactase-phlorizin hydrolase in transfected polarized Madin Darby canine kidney cells using metabolic labeling and sucrose-density centrifugation analysis. We detected high mannose dimers of the lactase-phlorizin hydrolase precursor molecule after metabolic labeling with [35S]methionine at 37 and 15 degrees C. In addition, both complex-glycosylated lactase-phlorizin hydrolase precursor molecule and the mature microvillus membrane-bound enzyme showed this oligomeric structure. Chemical crosslinking resulted in the detection of covalently crosslinked lactase-phlorizin hydrolase dimers after sodium dodecyl sulfate polyacrylamide gel electrophoresis. These results provide evidence that oligomerization of lactase-phlorizin hydrolase is an early event and begins in the endoplasmic reticulum.
 ...
PMID:Human lactase-phlorizin hydrolase: evidence of dimerization in the endoplasmic reticulum. 748

The capacity of intestinal lactase (EC 3.2.1.23) of piglets to hydrolyse lactose in vivo was investigated by measuring the response of blood galactose to doses of lactose, galactose plus glucose and both whole and skimmed milk. Following the administration of oral doses of lactose dissolved in water to piglets from 2 to 18 d of age the adjusted galactose area under the curve (AUC) was between 1.12 and 1.36 arbitrary units, while following a dose of galactose plus glucose dissolved in water it was between 1.56 and 1.98 arbitrary units. Whereas these results suggest that the rate of digestion of lactose appeared to limit the amount of galactose reaching the peripheral blood after a dose of lactose dissolved in water, there was no significant correlation between the capacity of piglets to hydrolyse physiological amounts of lactose and the age of the piglets (2- to 18-d-old piglets; r 0.11). Following oral doses of sow's milk containing either lactose, or galactose plus glucose, the adjusted galactose AUC values were 0.94 and 1.00 arbitrary units respectively, in 10-d-old piglets. Thus, the limitation to the digestion of lactose observed when it was present in water was not evident for lactose in sow's milk. Since there was no significant difference between the adjusted galactose AUC following a dose of whole milk (0.95 arbitrary units) and that following a dose of skimmed milk (1.03 arbitrary units), the presence of fat in sow's milk did not appear to affect the utilization of lactose by the sucking piglets.
 ...
PMID:The responses of blood galactose to oral doses of lactose, galactose plus glucose and milk to piglets. 762 93

Milk lactose is hydrolysed to D-galactose and D-glucose in the small intestine of mammals by the lactase-phlorizin hydrolase complex (LPH, EC 3.2.1.23-62). Lactase activity has broad substrate selectivity and several glycosides are substrates. Recently, using the monodeoxy derivatives of methyl beta-lactoside (1), we have shown the importance of each hydroxyl group in the substrate molecule concerning the interaction with the enzyme. Now we have studied the corresponding O-methyl derivatives, as well as some of the halo derivatives of 1. We have found that the enzyme presents steric restrictions to the recognition of substrates modified in the galactose moiety. In contrast, the binding site for the aglycon part of the substrate is looser. On the other hand, we have previously shown that HO-3' and HO-6 were important for the recognition of the substrate by the enzyme. Now we have found that the corresponding fluorine derivatives are not, or very poorly, recognized. This suggests that the HO-3' and HO-6 participate, as donors, in hydrogen bonds in the interaction with the enzyme.
 ...
PMID:Substrate specificity of small-intestinal lactase: study of the steric effects and hydrogen bonds involved in enzyme-substrate interaction. 764 81

Conscious unrestrained piglets were fasted overnight and infused intravenously with [2H3]leucine for 6 h. Sucrase isomaltase and lactase phlorizin hydrolase were immunoprecipitated from jejunal mucosal membranes, and the immunoprecipitates were electrophoresed on polyacrylamide gels. Bands corresponding to the pro and mature isoforms of both enzymes were acid hydrolyzed. [2H3]leucine isotopic enrichment was measured by gas chromatography-mass spectrometry using negative chemical ionization. Plasma leucine reached isotopic steady state within 90 min. The isotopic enrichment of mucosal leucine was 73% of that of plasma leucine. The high mannose and complex glycosylated forms of prolactase were in isotopic equilibrium, and their isotopic enrichment was 94% of mucosal leucine. The fractional synthesis rates of total and membrane protein were 0.45 and 0.65 days-1, whereas the processing rates of mature lactase, sucrase, and isomaltase were 0.90, 0.23, and 0.21 days-1, respectively. Approximately 65% of the label in the sucrase isomaltase immunoprecipitate was in the complex glycosylated precursor, whereas 73% of the label in lactase phlorizin hydrolase was in the mature (160 kDa) form. We conclude that the low rate of brush-border sucrase synthesis reflects a slow rate at which the complex glycosylated precursor is processed to the brush-border form.
 ...
PMID:Brush-border disaccharidase synthesis in infant pigs measured in vivo with [2H3]leucine. 781 Jun 60


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>