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:3.2.1.26 (invertase)
4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During the degradation of intestinal sucrase-isomaltase by pancreatic proteinases, degradation of sucrase-active site precedes that of the isomaltase-active site in rats. In the present paper, we demonstrate that the extent of degradation of sucrase-isomaltase is altered by dietary manipulation in vivo. Adult rats were starved for 24 h and received either a standard diet (20 cal% protein, 55% carbohydrate) or an isocaloric high-protein, low-carbohydrate diet (70 cal% protein, 5% carbohydrate). Animals were killed 15 h after the refeeding. In rats fed a high-protein, low-carbohydrate diet, luminal trypsin activity was three times higher than controls, and sucrase activity in proximal ileum was significantly lower (P less than 0.001) than controls, whereas isomaltase activity was similar in both groups. In proximal jejunum, luminal trypsin activity was remarkably lower (P less than 0.01) than in proximal ileum in both groups; sucrase and isomaltase activity was similar in both groups. Crossed immunoelectrophoresis demonstrated that a degradation product of sucrase-isomaltase, i.e., isomaltase monomer, was present in a larger amount in rats fed a high-protein, low-carbohydrate diet. In rats with bypassed pancreatic ducts, the amount of this degradation product was decreased and effect of a high-protein, low-carbohydrate diet was abolished. Experiments with a sequential isolation of epithelial cells of proximal ileum revealed that sucrase activity was decreased along the entire height of the villus in animals fed a high-protein, low-carbohydrate diet.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of a high-protein, low-carbohydrate diet on degradation of sucrase-isomaltase in rat jejunoileum. 328 54

Yeast secretory mutant sec53 cells accumulate inactive secretory glycoprotein precursors that remain associated with the endoplasmic reticulum (ER) at the restrictive temperature (37 degrees C). The possibility that precursor polypeptides fail to penetrate completely into the ER lumen was tested by examining the protease accessibility of accumulated invertase, mating pheromone precursor prepro-alpha-factor and the vacuolar protein precursor procarboxypeptidase Y in cell lysates. In all three cases, the secretory protein precursors are protected from the action of exogenous protease unless the membrane is permeabilized by including Triton X-100 or saponin in the incubation. These results suggest that the sec53 defect allows complete polypeptide translocation. Consistent with this interpretation, the precursor of invertase accumulates in a signal peptide-processed form. In addition, invertase and prepro-alpha-factor precursors contain a small amount of possibly aberrant carbohydrate. In mutant cells or in wild type cells treated with tunicamycin, a 10-kDa fragment of the N terminus of mature invertase assumes a conformation that is resistant to trypsin with or without detergent. This domain may be associated with an ER protein or may simply assume an unusual conformation as a consequence of deficient glycosyl modification.
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PMID:Product of SEC53 is required for folding and glycosylation of secretory proteins in the lumen of the yeast endoplasmic reticulum. 329 55

In the pigeon, 70-80% of the activities of maltase (alpha-D-glucoside glucohydrolase EC 3.2.1.20), sucrase (alpha-glucohydrolase, EC 3.2.1.48), isomaltase (dextran 6-alpha-D-glucan hydrolase, EC 3.2.1.10) and glucoamylase (1,4-alpha-D-glucan glucohydrolase, EC 3.2.1.3) were found to be localized in the brush-border membrane of intestinal epithelial cells. Of the total glycosidase activities in the mucosal homogenate, nearly 60 to 70% were recovered in the microsomal (105 000 X g) fraction, about 30% in the mitochondrial (22 000 X g) fraction and less than 5% from the cytosol (105 000 X g supernatant) fraction. The hydrolases were solubilized by digestion with papain but not with trypsin, and the phosphate ion had a protective effect in the solubilization. Amongst detergents, Triton X-100 but not sodium deoxycholate, was found to truly solubilize these enzymes.
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PMID:Studies on the intestinal disaccharidases of the pigeon. II. Subcellular localization and solubilization. 618 28

It has been demonstrated by the methods of histochemical and biochemical examination of the activity of the enzymes that the mucus layer covering the small intestinal wall contains active enzymes (alkaline phosphatase, leucin aminopeptidase IV, saccharase, lactase) and pancreatic enzymes (alpha-amylase and trypsin). Emphasis is laid on the enrichment of the mucus layer with pancreatic enzymes as compared with small intestinal juice. A hypothesis has been advanced according to which the mucus layer undergoes degradation of polymeric and oligomeric substrates, which plays a physiological part in the digestion of nutritive substances and protection of the internal medium against immunoactive biopolymers. The digestion occurring in the mucus layer is proposed to be called mucus digestion.
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PMID:[Enzymes in the mucosal layer of the small intestine]. 619 54

The results presented show striking differences in the response of the exocrine pancreas to fasting in suckling versus adult rats. In adult rats, fasting led to an increase in lipase to amylase ratio with a particularly sharp decrease in amylase concentrations, a generalized decrease in total protein, amylase, trypsinogen and lipase contents, and a decrease in responsiveness of the pancreatic acini to optimal and supraoptimal concentrations of secretagogues in vitro. In 15 day old pups, however, fasting led to an increase in total amylase, trypsin and lipase and a maintenance of the total protein content in their pancreases. Further, no decrease in responsiveness of their pancreatic acini to secretagogue stimulation is observed at the concentrations studied. The difference in the behavior of the exocrine pancreas during fasting can be partly explained by the changing pattern of their responses to hormonal stimulation, particularly that of corticosterone and cholecystokinin during various stages of development. Fasting led to an increase in corticosterone and presumable decrease in cholecystokinin. The pancreas of the suckling rat is very sensitive to the induction effect of corticosterone while that of the adult rats is relatively insensitive. Conversely, the pancreas of the adult rats is sensitive to the trophic effect of cholecystokinin while that of the suckling rat has the opposite reaction. The combination of these and other factors then resulted in an entirely different profile of the responses of the exocrine pancreas to fasting. Recent studies in our laboratory, and that of others, showed that an analogous situation also existed in the small intestine. Fasting of adult rats led to a general decrease in small intestinal enzymes including sucrase and maltase (29) but in suckling rats led to (30,31) increases of sucrase and maltase. Corticosterone again has been shown to be involved (30,31). Further, the small intestinal sucrase of the suckling rats responded to corticosterone by an increase in its level but the same hormone did not seem to control the sucrase concentrations in the small intestine of adult rats (32,33). Thus, both the small intestine and the pancreas responds very differently to fasting presumably mediated through a varying pattern of responses to selective hormonal stimulation, eg in this case, corticosterone. These results strongly suggest the importance of the interaction between environmental influences (fasting in this case) and the stage of development in determining the outcome of ontogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Response of the pancreas to fasting: adult versus neonates. 620 75

The appearance and continuing growth of extracellular material on Streptococcus mutans HS6 cells in sucrose-containing Merthiolated buffer was observed in a scanning electron microscope and was found to be related to the glucan synthesis on the cell and to adherence of the cell to a smooth surface. Cells grown in broth completely deprived of sucrose by invertase (HS6-IV) had a characteristic, slightly rugged surface structure. On incubation of HS6-IV in the sucrose-containing buffer, a few small globular particles appeared on the surface and grew to an irregular shape (globular to fibrilar) after several hours. The increase in the total glucan content of the cells paralleled the growth of the globular material, to which ferritin-conjugated anti-dextran globulin was found to bind. On the cell surface of cells harvested from conventional broth, both small globular and irregular structures, which possibly formed from sucrose in the broth, existed originally and continued to grow during incubation, along with the material newly appearing on the surface. The accumulation of glucan on the cells resulted in their adherence to a glass surface. The inhibition of growth of the extracellular material on the cells by trypsin, dextranase or anti-glucosyltransferase corresponded to the decrease in glucan synthesis and the loss of adhering ability. These results indicated that the material growing on the cell surface was glucan synthesized by glucosyltransferases.
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PMID:Synthesis of glucan on the cell surface of Streptococcus mutans: chemical and scanning electron microscopic studies. 621 5

Yeast secretory mutants sec53 and sec59 define a posttranslational stage in the penetration of glycoprotein precursors into the endoplasmic reticulum (ER). In the previous report we showed that at the restrictive temperature (37 degrees C) these mutants accumulate enzymatically inactive and incompletely glycosylated forms of the secretory enzyme invertase and the vacuolar enzyme carboxypeptidase Y. Cell fractionation experiments reveal that these precursor forms remain firmly bound to the ER membrane. However, upon return to the permissive temperature (24 degrees C), the invertase precursors are glycosylated, become partially active, and are secreted. Thermoreversible conversion does not require protein synthesis, but does require energy. In contrast to the effect of these mutations, inhibition of oligosaccharide synthesis with tunicamycin at 37 degrees C causes irreversible accumulation of unglycosylated invertase. The effect of the drug is exaggerated by high temperature since unglycosylated invertase synthesized in the presence of tunicamycin at 25 degrees C is secreted. A portion of the invertase polypeptide accumulated at 37 degrees C is preserved when membranes from sec53 and sec59 are treated with trypsin. In the presence of Triton X-100 or saponin, the invertase is degraded completely. The protected fragment appears to represent a portion of the invertase polypeptide that is embedded in or firmly associated with the ER membrane. This association may develop early during the synthesis of invertase, so that in the absence of translocation, some of the completed polypeptide chain remains exposed on the cytoplasmic surface of the ER.
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PMID:Genes required for completion of import of proteins into the endoplasmic reticulum in yeast. 636 72

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 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

Amylase, alpha- and beta-glucosidase, alpha- and beta-galactosidase, beta-fructosidase, trypsin, aminotripeptidase, leucine-aminopeptidase, prolinase, prolidase glycyl-L-leucine dipeptidase and glygylglycine dipeptidase are present in the 3rd instar larvae of Chilo auricilius.
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PMID:Digestive enzymes in the gut and salivary gland of the larvae of Chilo auricilius Ddgn. 698 21


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