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)

1. Change in digestive enzyme activities determined biochemically in brush-border membrane vesicles and cytochemically in isolated villi of lamb proximal intestine has been related to diet, intestinal structure and rumen development during the first 10 weeks of postnatal life. 2. Lactase activity halved, dipeptidylpeptidase IV activity doubled and aminopeptidase N and alkaline phosphatase activities remained constant during this period of development. Maintaining lambs on a milk replacer diet for 5 weeks after birth had no effect on this pattern of postnatal change in digestive enzyme activities. 3. Structural changes accompanying these selective effects on enzyme expression included a halving of villus height and a doubling of villus width. Villus surface area remained unaffected by these changes in height and width of villi. Crypt depth doubled during the first 10 weeks of postnatal life. Maintaining lambs on a milk replacer diet for 5 weeks did not affect this pattern of change in intestinal structure. 4. It appears from these results that postnatal decrease in lactase and increase in dipeptidylpeptidase IV activities are not regulated by factors such as diet, rumen development, or changes in intestinal structure. Attention is drawn to differences encountered between these results and a postnatal modification of glucose transport which clearly is dependent on diet.
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PMID:Postnatal development of lamb intestinal digestive enzymes is not regulated by diet. 190 59

The effects of long-term starvation on the activities of sucrase, lactase, and aminopeptidase, and on their respective mRNA were determined in the small intestine of thyroidectomized and sham-operated adult rats. Thyroidectomy reduced the protein loss at the level of the intestinal brush border membranes during starvation. Prolonged fasting caused a significant decrease in sucrase activity, but thyroidectomy partly prevented this effect. However, the amount of the corresponding mRNA dropped during long term starvation without incidence of thyroidectomy. Lactase activity in the brush border membranes was increased by starvation, and thyroidectomy caused a further elevation of the enzyme activity. Simultaneously, lactase mRNA content rose only slightly compared to the enzyme activity. Aminopeptidase activity and mRNA content decreased during starvation and thyroidectomy did not prevent this process. These results indicate that intestinal hydrolases respond non-coordinately to long-term food deprivation. In addition, the thyroid status of the animals has a direct influence on the adaptation of several brush border hydrolases to starvation. This suggests that the drop in plasma thyroid hormones during fasting allows a better maintenance of protein content and of hydrolase activities in the brush border membranes of the small intestine. These adaptive processes seemed to be partly controlled at a post-transcriptional level.
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PMID:Adaptation of intestinal hydrolases to starvation in rats: effect of thyroid function. 193 43

The in vitro effects of human duodenal secretions and various combinations of its components on activity and release of enzymes from the human brush border were examined. Sucrase retained activity for 90 min in duodenal secretions, and maltase was almost as stable; lactase lost activity rapidly and alkaline phosphatase was of intermediate stability. Inactivation of lactase could only be partly (50%) attributed to luminal proteases, bile salts and phospholipids played no role. Rate of release of an enzyme from the brush border bore no relationship to its rate of inactivation. When individual proteases were studied, elastase was the most potent for releasing disaccharidases from the brush border; trypsin was ineffective alone but augmented the effect of elastase. Sucrase and maltase were activated by proteolytic release, but activation was abolished by simultaneous exposure of brush borders to bile salts. Lactase was released and rapidly inactivated by proteinases, while alkaline phosphatase appeared to be inactivated without significant release. These results show that there are significant interactions between luminal factors which have been inapparent when studying them in isolation. Loss of functionally useful enzyme does not follow release of sucrase or maltase from the brush border into the lumen but does follow release of lactase. Study of the susceptibility of lactase to inactivation by luminal factors in the various forms of lactose intolerance is warranted.
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PMID:Influence of duodenal secretions and its components on release and activities of human brush-border enzymes. 210 71

Brush border lactase, sucrase and glucoamylase activities were assessed in jejunal mucosal biopsy specimens from 34 children (median age 11 months; range 1.5-38) having protracted diarrhoea with failure to thrive and 8 well nourished children with normal jejunal mucosal histology (median age 10.2 months; range 2-37). All enzymes showed progressive decrease in activity which was directly in relation to increasing degree of mucosal injury (P less than 0.002). Lactase was significantly reduced even in patients with protracted diarrhoea and normal mucosa (P less than 0.05). Glucoamylase and sucrase were significantly reduced only in the presence of mucosal injury (P less than 0.01). Our data suggest that most children with protracted diarrhoea may not tolerate lactose containing feeds and may need lactose-free diets preferably based on starch. A small number of children with protracted diarrhoea, who have severe mucosal injury may not be able to handle even starch and may require diets based on short chain glucose polymers. The findings of this study, need to be corroborated with well-controlled metabolic balance studies.
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PMID:Intestinal glucoamylase & other disaccharidases in children with protracted diarrhoea. 211 15

All neonates are born with intestinal lactase activity. In most of them the intestinal lactase activity is lost during childhood (lactase restriction phenotype). In a minority of children normal intestinal lactase activity is retained (lactase persistence phenotype). In this study the progression of the lactase restriction phenotypes has been studied in 94 Sri Lankan children by oral lactose loads and 162 British children by intestinal lactase estimation (adult Sri Lankans and British predominantly belong to the lactase restriction and lactase persistence phenotypes, respectively). Lactase was present in infancy at birth in all Sri Lankan children and declined around the age of eight years, the majority (59 per cent) of the 10-15-year-olds belonging to the lactase restriction phenotype. In contrast the majority of the British children (95 per cent of all the British children studied) demonstrated the lactase persistence phenotype. The low prevalence rate of the restriction phenotype found among British children was largely contributed by children of African and Asian origin.
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PMID:Age dependency of the lactase persistence and lactase restriction phenotypes among children in Sri Lanka and Britain. 211 2

The relationship between obesity and the digestion of carbohydrates is poorly understood. Data in humans have provided conflicting results. Studies using the obese mouse (C57BL/6Jobob) suggest that obesity is associated with increased activity of intestinal alpha-disaccharidases. To evaluate the developmental pattern of these enzyme activities in obesity, we determined the activity of sucrase and lactase in the small intestine of genetically obese mice (C57BL/6Jobob) and lean littermates at 3 and 10 weeks of age. Sucrase and lactase activities were measured on intestinal homogenates from segments of the small intestine in mice maintained on standard laboratory diets during the postweaning period. Results were expressed as specific activity and total activity per intestinal segment. Obese mice did not differ from lean littermates in body weight at 3 weeks of age, but exhibited increased protein content in the proximal small intestine. Sucrase specific activity was significantly higher in the obese mice at 3 weeks of age in all intestinal segments. Sucrase total activity showed a similar pattern. At 10 weeks of age, body weights of obese mice were substantially greater than the lean littermates. Sucrase specific and total activities were also greater in the obese mice at 10 weeks of age. Lactase specific activity, however, was similar in both obese and lean mice at both ages studied. Lactase total activity was greater in the obese mice, consistent with their greater intestinal mass. These observations demonstrate that changes in the intestinal sucrase activity of the obese mouse precede the development of excessive body weight.
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PMID:Age-related changes in sucrase and lactase activity in the small intestine of 3- and 10-week-old obese mice (C57BL/6Jobob). 211 45

Endoscopic duodenal biopsy specimens from 100 predominantly adult Caucasian patients under investigation for gastrointestinal symptoms were used to establish reference ranges for lactase, sucrase, and maltase in the duodenum. Duodenal and jejunal disaccharidase values were compared and the association between disaccharidase activity and morphology in the duodenum was examined. Mean lactase activities were about 40% lower in the duodenum compared with the jejunum; maltase was reduced to a lesser extent; and sucrase activities were much the same in the two sites. Lactase deficiency was found in 24 patients of whom 14 (58%) had duodenal disease. The presence of moderate to severe duodenal lesions was associated with a significant decrease in all disaccharidase activities, while only lactase was reduced in mild lesions. Twelve patients had normal lactase activity, despite the presence of duodenal disease. It is concluded that specific reference ranges for duodenal mucosal disaccharidase activity are required as this is less than that of jejunum. Reduced duodenal disaccharidase activity is usually but not invariably associated with morphological abnormality.
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PMID:Activity of duodenal disaccharidases in relation to normal and abnormal mucosal morphology. 211 56

The mechanism of decline in the catalytic activity of intestinal lactase during neonatal maturation has not been defined, but a shift in the lactase subunit synthesis from an active 130-kDa subunit to an inactive 100-kDa species has now been noted in the adult rat (Quan, R., Santiago, N. A., Tsuboi, K. K., and Gray, G. M. (1990) J. Biol. Chem. 265, 15882-15888). The subunit structure, synthesis, intracellular assembly, and subsequent degradation of lactase from the brush-border surface membrane was examined in 15-day-old pre-weaned and 30-day-old post-weaned intact rats. Lactase was labeled intraintestinally with [35S]methionine, isolated from Triton-solubilized membranes with monospecific polyclonal anti-lactase, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The protein-stained gel revealed subunits of 225 and 130 kDa, the latter species predominating in both the pre- and post-weaned state. The distinct adult-type 100-kDa moiety was present in post-weaned animals while only a trace of a slightly larger (approximately 110 kDa) species was observed in pre-weaned animals. Quantitation of radioactivity in newly synthesized lactase revealed an increasing prominence of the 100-kDa species in post-weaned rats (130/100 incorporation ratio: pre-weaned 6.2; post-weaned 3.3). Accumulation of newly labeled lactase in brush-border membranes after intraperitoneal [35S]methionine labeling was similar in both groups at 3 h. Despite these comparable rates of lactase synthesis, assembly and insertion in the pre- and post-weaned state, subsequent removal of the 130-kDa unit was more rapid in post-weaned animals (t1/2 = 11 h; pre-weaned t1/2 = 37 h). In intact rats, the neonatal maturational decline in lactase catalytic activities involves both a shift to production of the inactive 100-kDa subunit and increased membrane surface degradation of the active 130-kDa subunit.
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PMID:Intestinal lactase in the neonatal rat. Maturational changes in intracellular processing and brush-border degradation. 211 33

Lactase (beta-D galactoside-galactohydrolase, E.C.3.2.1.23) is a relevant enzyme to the dairy industry as it modifies undesirable functional and nutritional properties derived from the lactose content in milk and dairies, and as a way of recovering or upgrading cheese whey. This latter aspect has been considered to develop an enzyme catalyst suitable for the continuous hydrolysis of whey permeate. The selection of enzyme and support and the immobilization procedure has been reported previously. Results obtained in the immobilization of fungal lactase on activated chitin have prompted us to scale-up the procedure, a system being developed in which the enzyme is immobilized within the reactor (in situ). Results are presented for the in situ immobilization of lactase with and without recirculation of the reagents. Previous procedure was reproduced, although moderate profiles of activity were generated through the catalyst bed which were not eliminated by recirculation. Packed bed reactors with immobilized lactase were operated at varying flowrates and lactose concentrations, results being compared, in terms of substrate conversion and reactor productivity, with a theoretical model based on the corresponding kinetic expression and ideal flow regime. Deviations are significant at high flowrates which is attributed to backmixing and channeling through the catalyst bed. The model fits reasonably well at low flowrates and high feed substrate concentration. Productivity was 58 g of glucose/l.h at 40 ml/h of 120 g/l of lactose. Stability of the immobilized lactase was assessed in long-term reactor operation with whey permeate (35 g/l of lactose) at 40 degrees C and pH 4.0. Operational half-life was 120 days.
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PMID:[Immobilization of microbial lactase]. 213 18

Lactase deficient subjects, who form the bulk of the world population, absorb yogurt lactose because the bacteria used for fermentation produce beta-galactosidase. From a milk fermented by these bacteria and dried by a temperature-controlled process a power could be obtained which possess residual lactase activity but, unlike yogurt, does not need storage at low temperature. The lactose of this fermented powdered milk is perfectly absorbed, as proved by hydrogen respiratory tests performed in 35 lactose intolerant African subjects living in isolated villages. In 25 malnourished children under 3 years of age, this milk allowed renutrition without inducing diarrhoea--a result which could not have been obtained with ordinary milk in two-thirds of the cases. This type of food is potentially valuable to feed the large population of the third world.
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PMID:[Use of a fermented powdered milk in malnourished or lactose intolerant children]. 213 60


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