Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.20 (alpha-glucosidase)
4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of various glycosidases in homogenates of the small-intestinal mucosa of one adult and two suckling echidnas, Tachyglossus aculeatus, were investigated. The activities of lactase (beta-D-galactosidase), beta-N-acetylglucosaminidase, neuraminidase and alpha-L-fucosidase were higher in the sucklings than in the adult animal. Maltase and isomaltase activities were lower. Sucrase and cellobiase activities were absent or present in trace amounts only. The lactase activity had a pH optimum of 4.0-4.5, was predominantly in the soluble fraction following ultracentrifugation and was inhibited by p-chloromercuribenzene sulfonate, suggesting that it was due to a lysosomal acid beta-galactosidase and not a brush-border neutral lactase. The maltase activity of the sucklings also had the characteristics predominantly of a lysosomal acid hydrolase. It is proposed that in suckling echidnas, the oligosaccharides (mainly neuraminyllactose and fucosyllactose) of the mother's milk are digested intracellularly by lysosomal enzymes, rather than at the brush border, of the epithelial cells of the small-intestinal mucosa.
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PMID:Intestinal glycosidase activities in one adult and two suckling echidnas: absence of a neutral lactase (beta-D-galactosidase). 641 47

These studies examined the potential for reorganization and differentiation of dissociated 18-day fetal rat intestine. Cultures of trypsin-dissociated fetal intestine were maintained in vitro for 1 week on a three-dimensional matrix, then transplanted into syngeneic hosts. When harvested after 4 weeks, these transplants consistently demonstrated organotypic differentiation. Spherical structures containing crypts with frequent mitotic figures and villi lined with columnar epithelium had formed. PAS staining demonstrated positive epithelial cell brush borders, goblet cells, and luminal contents. Significant levels of the microvillus membrane enzymes lactase, sucrase, maltase, and alkaline phosphatase were present in the luminal contents. Sucrase-isomaltase, an enzyme characteristic of postweaning small intestine, was demonstrated by immunoprecipitation and SDS-PAGE. Thus, both morphological and biochemical maturation occurred in the transplants.
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PMID:Organotypic differentiation of trypsin-dissociated fetal rat intestine. 661 90

The enzyme responsible for all of the isomaltase activity and much of the maltase activity in the small intestine of the Californian sea lion (Zalophus californianus) was isolated by detergent solubilization of the brush-border membrane, followed by immunoadsorption chromatography using antibodies directed against rabbit sucrase-isomaltase. In 0.1% Triton X-100, sea lion isomaltase occurs as a monomer of Mr = 245,000 and is composed of a single polypeptide chain. As judged from the stoichiometry of the covalent binding of the affinity label, conduritol-B-epoxide, this polypeptide chain carries two enzymatically active sites; they are apparently identical and do not show either positive or negative cooperativity. In addition to cross-reacting immunologically with rabbit sucrase-isomaltase, sea lion isomaltase has similar overall enzymatic properties, with the exception of not hydrolyzing sucrose. The Alaskan fur seal (Collarhinus ursinus) has a two-active site isomaltase; however, in contrast to the sea lion, this animal is endowed with a small but significant sucrase activity. Along with (fully active) pro-sucrase-isomaltase, sea lion isomaltase is one of the very few examples of enzymes with more than one active site on a single polypeptide chain acting "in parallel" (rather than "in series"). Furthermore, this enzyme triggers some interesting questions on the phylogenetical pedigree of small intestinal sucrase-isomaltase.
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PMID:A two-active site one-polypeptide enzyme: the isomaltase from sea lion small intestinal brush-border membrane. Its possible phylogenetic relationship with sucrase-isomaltase. 671 26

It was investigated whether sucrase and isomaltase form an enzyme-enzyme complex in chick intestine or not, and some properties of the disaccharidases were compared with those of other species. 1) Chick intestinal sucrase and isomaltase were shown to exist in the form of an enzyme-enzyme complex from the results of polyacrylamide disc gel electrophoresis, DEAE Sephadex A-25 ion exchange column chromatography and citraconylation, although the chick intestinal sucrase and isomaltase were not retained on a Sephadex G-200 column. 2) The molecular weights of sucrase-isomaltase complex, maltase I, maltase II, maltase III and isomaltase dissociated from sucrase-isomaltase complex were estimated to be 250,000, 250,000, 160,000, 225,000 and 80,000, respectively, by polyacrylamide disc gel electrophoresis. 3) The optimum pH for all the enzymes was 6.0. 4) Km values of sucrase, isomaltase, maltase I and maltase III were 10.0, 3.5, 1.0 and 4.6 mM, respectively. Vmax values for sucrase, isomaltase, maltase I and maltase III were 217.4, 281.4, 147.1 and 454.5 mumol substrate hydrolyzed/mg protein/hr, respectively.
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PMID:Demonstration of sucrase-isomaltase complex in chick intestine. 676 9

The development of alkaline phosphatase, maltase, and sucrase activities in the duodenum of the chick embryo was followed in organ culture in chemically defined medium; 14-day duodenum was used in most experiments, with comparisons being made with 18-day tissue. As has been previously shown for the other enzymes, sucrase activity also rises at an accelerated rate in vitro. Since chick sucrase has maltase activity, its increase appears to account for the spontaneous rise of maltase activity; the form of maltase devoid of sucrase activity seems not to be accelerated. Sucrase, sucrase-free maltase, and alkaline phosphatase are all elevated by the addition of insulin to the medium. Intestinal sucrase is well known to be responsive to hydrocortisone, but it has now been found to be unresponsive to thyroxine, except that its dissociation from the brush border is increased at hormone concentrations above 1 nM. Insulin and thyroxine act synergistically on alkaline phosphatase, but the addition of hydrocortisone diminishes the effect of the other two. With sucrase, insulin and hydrocortisone have a synergistic effect which is intensified by addition of thyroxine. The previously demonstrated influence of hydrocortisone on maltase is accounted for by the maltase activity of sucrase. In combination, however, hydrocortisone and thyroxine elevated maltase much more strongly than sucrase, and the highest maltase levels were attained when all three hormones were present.
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PMID:Chick embryo intestine in culture: influence of insulin and other hormones on sucrase, maltase, and alkaline phosphatase. 676 10

The sensitivity of human intestinal lactase to pancreatic proteases was tested both in vitro and in vivo. Lactase specific activity in brush border membranes was decreased by 26%-27% during incubation with trypsin at pH 7.0 in patients with normal intestinal lactase levels, whereas in patients with lactase deficiency the inactivation was 75%. However, when lactase levels from deficient patients' mucosa were increased relative to trypsin during incubation so that they were comparable to the levels of activity in normal mucosa, inactivation of lactase in deficient patients was only 45%. Therefore, in these patients the greater in vitro lactase inactivation by trypsin could be explained at least in part by an increased trypsin/lactase ratio. Sucrase levels were decreased in vitro by trypsin (about 40%), but maltase activity was unaffected. The effect of pancreatic proteases was tested in vivo in patients with pancreatic insufficiency. After the addition of pancreatic enzymes (Viokase), lactase specific activity fell by 16% in patients with normal lactase, and by 38.5% in patients with lactase deficiency. In both groups of patients, lactase levels fell to a greater extent than did sucrase or maltase. These data demonstrate that pancreatic proteases can alter intestinal lactase activity in humans. Moreover, in lactase-deficient patients, lactase activity decreases to a greater extent than in patients with normal lactase, resulting in further deficiency of this enzyme.
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PMID:Effect of pancreatic proteases on intestinal lactase activity. 677 5

Effect of bilateral adrenalectomy and subsequent injections of hydrocortisone and pentagastrin on the activity of different intestinal digestive enzymes were measured in 20-day-old rats. Eleven days after adrenalectomy the activity of lactase, sucrase, and alkaline phosphatase, but not maltase, was significantly decreased when compared with sham-operated rats. In adrenalectomized rats, repeated injections of hydrocortisone (50 mg/kg) significantly increased the activity of lactase, sucrase, maltase, and alkaline phosphatase by 15%, 49%, 32% and 121%, respectively, over the corresponding adrenalectomized control. Pentagastrin (500 microgram/kg) injections to adrenalectomized rats produced significant 41% and 58% increments in lactase and alkaline phosphatase activities, compared with the adrenalectomized control. Sucrase activity was unaffected by pentagastrin, but maltase showed a non-significant 34% higher activity than in the adrenalectomized control. Adrenalectomy by itself lowered the Km and Vmax of alkaline phosphatase by 33% and 66%, respectively, which were increased to 95% and 70% of the corresponding sham-operated level by either hydrocortisone or pentagastrin treatment. When intestinal homogenates from salinetreated adrenalectomized rats were mixed in equal proportion with homogenates from sham-operated or hydrocortisone- or pentagastrin-treated animals, Km values for alkaline phosphatase were found to be similar to those observed for sham-operated or hormone-treated groups alone. However, in the same mixed preparations Vmax values were found to be additive.
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PMID:Effects of hydrocortisone and pentagastrin on the activity of intestinal disaccharidases and alkaline phosphatase in weanling rats. 679 41

A leukemic mouse model was employed to elucidate the separate effect of leukemia and cytotoxic drugs on the jejunal mucosa and its associated digestive enzymes. The mitotic activity, depth of the crypt and villus-crypt quotient were not significantly changed in leukemic mice in comparison to normal mice. The mitotic activity and the depth of the crypt 48 h after 20 mg methotrexate (MTX)/kg were significantly reduced (p less than 0.01) in leukemic mice. Sucrase (p less than 0.001) and maltase (p less than 0.025) activities in the jejunum from leukemic mice were significantly elevated in comparison with non-leukemic controls. In both non-leukemic and leukemic mice, the dose-response curves for MTX administration revealed a significant decrease and a nadir in sucrase (p less than 0.001) and maltase (p less than 0.0025) activities at the dosage of 20 mg/kg. Thus, in the mouse model, leukemia per se does not contribute to significant diminution in small intestinal function. In the small intestine, MTX appears to be responsible for a decrease in the mitotic activity of crypt cells, depth of the crypt and diminished sucrase and maltase activities.
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PMID:Effect of leukemia and methotrexate on digestive enzymes in the jejunum of mice. 701 77

Experimentally induced diabetes enhances the specific activity of several microvillus membrane proteins in the rat small intestine. The increase in the specific activity of sucrase-isomaltase has been shown by others to be due to an increase in enzyme protein, raising the possibility that diabetes induces a generalized increase in microvillus membrane proteins. Since intramembrane particles (IMPs) seen on freeze-fracture replicas of microvillus membranes are thought to represent integral membrane proteins, we compared microvillus IMP densities in diabetic rats with those in control rats. In addition, mucosal sucrase, maltase, and alkaline phosphatase specific activities were measured in all animals. Diabetic rats had significantly increased sucrase and maltase but not alkaline phosphatase specific activities compared with control rats. The density of microvillus IMPs on both the protoplasmic and extracellular fracture faces of undifferentiated crypt cells and villus absorptive cells was not increased in experimental diabetes. These data indicate that diabetes does not result in a generalized increase in microvillus membrane proteins. Thus the enhanced activity of microvillus membrane proteins in diabetes appears to be highly selective.
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PMID:Structural features of the rat small intestinal microvillus membrane in acute experimental diabetes. 704 26

The effect of resuming food intake after a period of starvation (refeeding) on the specific activities of selected rat intestinal enzymes was determined. The rate of weight gain was higher in refed animals than in control animals, without a difference in food intake. Fasting caused intestinal atrophy which reversed rapidly on refeeding. Fasting decreased the specific activities of sucrase, maltase, and galactokinase, but did not affect the specific activities of hexokinase, pyruvate kinase, or crypt thymidine kinase. Sucrase, maltase, hexokinase, pyruvate kinase, and thymidine kinase specific activities all rose above control values during refeeding. The overshoot in intestinal enzyme specific activities may help promote the rapid weight gain observed in refed rats and is an integral part of the total adaptation to fasting and refeeding.
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PMID:Refeeding after a fast in rats: effects on small intestinal enzymes. 705 2


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