Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of oral refeeding after total parenteral nutrition (TPN) on brush border hydrolases was measured in the proximal jejunum and ileum of adult rats. The animals received intravenously for 4 days a mixture of Intralipid 10% and Vamine-Glucose. At the end of TPN, oral feeding was reinstituted and the rats were fed with an isocaloric standard diet (60% carbohydrate, 17% protein, 3% lipid). Sucrase, isomaltase, lactase, and aminopeptidase N activities were measured at the end of TPN and at 1, 3, and 5 days after TPN. Sham-operated rats nourished orally with the standard diet were used as controls. In both intestinal segments, lactase activity showed no significant changes at the end of TPN or during oral realimentation. Isomaltase, and especially sucrase activities, exhibited an important drop at the end of TPN. After TPN, a complete restoration of isomaltase and sucrase activities was obtained in the jejunum only. During oral refeeding a 40% deficit in sucrase activity persisted in the ileum throughout the experimental period, whereas normal isomaltase activity was restored in this segment. Aminopeptidase N activity was lowered by TPN and recovered normal values within a few hours after oral realimentation. Thus, reinstitution of oral feeding after TPN should take into account that the intestine is capable of digesting normal amounts of dietary protein but has a reduced tolerance for carbohydrates.
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PMID:Imbalance between jejunum and ileum in the response of brush border hydrolases to oral feeding after intravenous alimentation in rats. 249 65

We describe a new and unique gastric carcinoma cell line (LIM1839) derived from a young Caucasian male with rapidly progressing disease. The cell line grows with a pleomorphic morphology and has been in continuous culture for more than 3 years. The cells cannot be cloned in semi-solid agar or grown in nude mice despite numerous attempts. The karyotype of the cultured cells is highly abnormal with a large number of structural and numerical changes. Some chromosomes are dicentric and this feature has persisted in this culture. The cells express one of the small-intestinal dipeptidases, aminopeptidase N, but do not express dipeptidyl peptidase IV or the disaccharidases, sucrase isomaltase or maltase glucoamylase. The cells express high levels of EGF receptors and of messenger RNA for insulin-like growth factor II.
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PMID:A new gastric carcinoma cell line (LIM1839) derived from a young Caucasian male. 260 77

gamma-Glutamyltranspeptidase (GGT), aminopeptidase N (AP-N), and sucrase in purified rabbit intestinal brush border membrane vesicles were irradiated in situ at -135 degrees C using high energy electrons. Surviving activities of the enzymes were measured as a function of radiation dose, and the functional unit target sizes (corresponding to carbohydrate-free polypeptides) were determined using target analysis. The in situ functional unit sizes were GGT 59 kDa, AP-N 59 kDa, and sucrase 63 kDa. Together with biochemical data determined previously, it is concluded that the noncovalently attached large (approximately 40 kDa) and small (approximately 25 kDa) subunits of GGT are both required for catalytic activity. Furthermore, these data suggest that (i) the membrane-bound form of AP-N consists of one or more noncovalently attached subunits of 59 kDa, each of which is enzymatically active; and (ii) in situ sucrase activity is associated with a subunit of 63 kDa which is noncovalently attached within the sucrase-isomaltase complex.
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PMID:Radiation inactivation probe of membrane-bound enzymes: gamma-glutamyltranspeptidase, aminopeptidase N, and sucrase. 288 May 26

The human colon cancer line Caco-2 exhibits after confluency a concomitant increase of glycogen accumulation and an enterocytic differentiation. The purpose of this work was to investigate whether forskolin (FK), an activator of adenylate cyclase, would induce a permanent glycogenolysis and, if so, whether it would result in modifications of the differentiation pattern of the cells. FK activates adenylate cyclase in Caco-2 cells with an ED50 of 7 X 10(-6)M. Three different treatment protocols with FK (10(-5)M) were applied: 1) the cells were treated during all the time in culture (20 days); 2) the treatment was started after confluency; 3) the treatment was interrupted after confluency. The presence of FK results in a permanent stimulation of cAMP accumulation (10 to 20 fold the basal values) and in a permanently reduced glycogen content (30 or 50% of the control values). The rates of glucose consumption are increased three and five fold in protocols 1 and 3 respectively. These metabolic changes are associated with morphological changes (tightening of the intercellular spaces and shortening of the brush border microvilli) and with a dual inhibition of the activities of brush border hydrolases: a) an inhibition of the post-confluent increase of activity of sucrase, aminopeptidase N and alkaline phosphatase in the brush border enriched fraction; b) an inhibition of the post-confluent increase of activity of sucrase in the cell homogenate. A comparison of the results obtained in each protocol shows that the morphological modifications and the decrease of the enzyme activities in the brush border fraction are regularly associated with an increased cAMP accumulation, whereas the inhibition of the differentiation of sucrase is a direct consequence of the increase in glucose consumption and decrease in glycogen stores.
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PMID:Enterocytic differentiation and glucose utilization in the human colon tumor cell line Caco-2: modulation by forskolin. 298 31

Effects of diet, hibernation and seasonal variations on hydrolase activities were determined in mucosa and purified brush border membranes of the small intestine of European hamsters. Wild hamsters captured in April and fed for several weeks with an equilibrated laboratory chow (20% protein, 50% carbohydrates) exhibited a rise in disaccharidase activities (sucrase, isomaltase, lactase) but no changes in aminopeptidase N activity. During deep hibernation, in contrast to sucrase and isomaltase activities which showed only minor changes, lactase activity was significantly enhanced along the jejunoileum, and aminopeptidase N activity was maximum in the ileum. After a short period (48 h) of wakefulness and feeding following 10 days of starvation during the hibernation period, the activities of the disaccharidases and of aminopeptidase N returned to values measured in active animals. In contrast to the nutritional state, which has an important impact on the activities of intestinal enzymes, season has little effect on the intestine of the active animal under a controlled environment. The pattern of enzyme activities which occurs along the small intestine in the hibernating animal may be a prerequisite for optimum digestion during the short phases of waking during the hibernation period of the European hamster.
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PMID:Adaptation of intestinal enzymes to seasonal and dietary changes in a hibernator: the European hamster (Cricetus cricetus). 317 Aug 22

The biogenesis of two microvillar enzymes, aminopeptidase N (EC 3.4.11.2) and sucrase (EC 3.2.1.48)-isomaltase (EC 3.2.1.10), was studied by pulse-chase labelling of pig small-intestinal explants kept in organ culture. Both enzymes became inserted into the membrane during or immediately after polypeptide synthesis, indicating that translation takes place on ribosomes attached to the rough endoplasmic reticulum. The earliest detectable forms of aminopeptidase and sucrase-isomaltase were polypeptides of Mr 140 000 and 240 000 respectively. These polypeptides were susceptible to treatment with endo-beta-N-acetylglucosaminidiase H (EC 3.2.1.96), suggesting that the microvillar enzymes during or immediately after completion of protein synthesis become glycosylated with a 'high-mannose' oligosaccharide structure similarly to other plasma-membrane and secretory proteins. After 20--40 min or 60--90 min of chase, respectively, aminopeptidase N and sucrase-isomaltase were reglycosylated to give the polypeptides of Mr 166 000 (aminopeptidase N) and 265 000 (sucrase-isomaltase). These were expressed at the microvillar membrane after 60--90 min. During the entire process of synthesis and transport to the microvillar membrane the enzymes were bound to membranes, indicating that the biogenesis of aminopeptidase N and sucrase-isomaltase occurs in accordance with the membrane flow hypothesis.
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PMID:Biosynthesis of intestinal microvillar proteins. Pulse-chase labelling studies on aminopeptidase N and sucrase-isomaltase. 612 70

Structural changes have been studied during the life cycles of three glycosidases: sucrase-isomaltase (EC 3.2.48-10), lactase-phlorizin hydrolase (EC 3.2.1.23-62), maltase-glucoamylase (EC 3.2.1.20); and three peptidases: aminopeptidase A (EC 3.4.11.7), aminopeptidase N (EC 3.4.11.2) and dipeptidyl peptidase IV (EC 3.4.14.5). The final forms of the enzymes can be divided into at least two groups: the sucrase-isomaltase type, characterized as dimers, which are asymmetric in their hydrophilic parts, have two types of active site and anchor only on one subunit; and the aminopeptidase N type, characterized as dimers, which are symmetric in their hydrophilic part, have only one type of active site and anchor on both subunits. These enzymes are likely to be synthesized on rough endoplasmic reticulum and simultaneously glycosylated into endoglycosidase H-sensitive forms. They are later reglycosylated to endoglycosidase H-resistant forms, which have relative molecular masses similar to the final forms. Enzymes of the sucrase-isomaltase type seem to be synthesized with a polypeptide-chain length corresponding to the sum of both subunits, whereas enzymes of the aminopeptidase N type seem to be synthesized with a polypeptide-chain length corresponding to the constituent subunits themselves. Not much is known about the catabolism of these enzymes. The enzyme activities and the amounts of enzyme protein decrease at the top of the villi, probably due to release into the lumen. The subunits of aminopeptidase N are cleaved by pancreatic proteases to smaller peptides, and sucrase-isomaltase may lose its sucrase polypeptide, while both enzymes remain bound to the membrane.
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PMID:Structure of microvillar enzymes in different phases of their life cycles. 613 6

The effect of monensin and colchicine on the biogenesis of aminopeptidase N (EC 3.4.11.2), aminopeptidase A (EC 3.4.11.7), dipeptidyl peptidase IV (EC 3.4.14.5), sucrase (EC 3.2.1.48)-isomaltase (EC 3.2.1.10) and maltase-glucoamylase (EC 3.2.1.20) was studied in organ-cultured pig small-intestinal explants. On the ultrastructural level, monensin (1 microM) caused an increasingly extensive dilation and vacuolization of the Golgi complex during 4h exposure of the explants. On the molecular level, the effect of monensin was twofold. (1) The processing from the initial high-mannose-glycosylated form to the mature complex-glycosylated form was arrested. For some of the enzymes studied, intermediate stages between the high-mannose and complex forms could be seen, probably corresponding to 'trimmed' or partially complex-glycosylated polypeptides. (2) Labelled microvillar enzymes failed to reach their final destination. These findings suggest the involvement of the Golgi complex in the post-translational processing and transport of microvillar enzymes. The presence in the growth medium of colchicine (50 micrograms/ml) caused a significant inhibition of the appearance of newly synthesized enzymes in the microvillar membrane during a 3 h labelling period. Since synthesis and post-translational modification of the microvillar enzymes were largely unaffected by colchicine, the results obtained suggest that microtubules play a role in the final transport of the enzymes from the Golgi complex to the microvillar membrane.
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PMID:Biosynthesis of intestinal microvillar proteins. Role of the Golgi complex and microtubules. 665 78

A method for analysing microgram amounts of microvillar membranes by two-dimensional electrophoresis (protein mapping) is described, and has been used to characterize the microvillar proteins of the small intestine of German shepherd, corgi, and beagle dogs. Detergent-solubilized microvillar membranes were radiolabelled with 14C and separated by isoelectric focussing followed by SDS-PAGE. Proteins were detected fluorographically and glycoproteins by lectin-affinity staining. The microvillar hydrolases alkaline phosphatase and dipeptidyl aminopeptidase IV were identified by active-site labelling and aminopeptidase N by immunoprecipitation. Changes following pancreatic duct diversion were consistent with accumulation of pro-sucrase-isomaltase and diminished expression of the sucrase and isomaltase subunits. Cytoskeletal proteins were concentrated in the core fraction remaining after extraction of microvillar membranes with Triton X-100. There were no consistent differences between dogs of different breed, and the canine protein maps were similar to the human.
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PMID:Characterization of microvillar membrane proteins of dog small intestine by two-dimensional electrophoresis. 758 24

Small intestinal epithelium digests and absorbs nutrients. Crypt stem cell transplantation can generate neomucosa with normal morphology, but the digestive and absorptive capacities of this neomucosa are unknown. This study evaluates stem cell induced neomucosal brush border digestive enzyme activity and nutrient transport function. Rodent small intestinal epithelial stem cells were isolated by enzymatic digestion, then grafted to inbred recipients. Grafts were retrieved at 25 days, and apical brush border membrane vesicles prepared for quantitative assays. Neomucosal lactase, sucrase, aminopeptidase N, and alkaline phosphatase activity was determined by incubation with enzyme specific substrate. Neomucosal sodium dependent D-glucose transport was evaluated by incubation with D-[U-14C] glucose. Comparative assays were performed in age-matched control intestine. Neomucosal digestive enzyme activities and D-glucose transport were all similar in neomucosa and control small intestine.
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PMID:Does neomucosa induced by small bowel stem cell transplantation have adequate function? 781 80


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