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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 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

Experiments were conducted to establish a stunting syndrome (SS) model to facilitate research on nutritional aspects of enteric disorders of poults. One-day-old turkeys were dosed per os with tryptose phosphate broth (TPB) (controls) or inoculum (inoculated). The inoculum was prepared by homogenizing intestines from 11-day-old commercial poults diagnosed to have SS in TPB (1:0.5 [wt:wt]). Subsequently, intestines from 8-day-old inoculated poults from the previous experiment were used. Inoculation reduced growth (P less than 0.001) and feed consumption (P less than 0.001) at 8 and 14 days of age. In Expts. 1, 2, and 3, gain of inoculated poults was 60.9%, 58.8%, and 52.6% that of controls up to 8 days of age and 77.9%, 76.6%, and 80.9% that of controls from 8 to 15 days of age, respectively. Feed conversion was impaired (P less than 0.001) up to 8 days of age. The activity of maltase and sucrase in the jejunum and of pancreatic enzymes was determined every 2 days up to 13 days of age. Inoculation decreased (P less than 0.001) maltase and sucrase starting at 3 days of age (i.e., maltase activity was 17.45 and 1.70 mumols maltose hydrolyzed/hr.mg protein in control and inoculated poults, respectively). Inoculation had no effect on pancreatic lipase, amylase, or trypsin.
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PMID:Stunting syndrome in turkeys. Development of an experimental model. 219 47

Studies were conducted to determine the in vitro effect of selected food components on activity of the brush border membrane pteroylpolyglutamate hydrolase (folate conjugase) of porcine and human intestine. Foods differed widely in their effects although the pattern of the effects on both porcine and human enzymes was similar. Extracts of legumes, tomatoes, and orange juice consistently inhibited the conjugase activity. Citrate was also inhibitory to some extent. In contrast, extracts of cereal grain flours, whole egg, milk, cabbage, cauliflower, and lettuce caused little inhibition. Purified phytohemagglutinins, soybean trypsin inhibitors, and bovine milk folate-binding protein had no effect on the conjugase activity at the concentrations tested. The food substances that inhibited the conjugase activity did not bind the polyglutamyl folate substrate or inhibit intestinal brush border membrane sucrase and alkaline phosphatase. These findings suggest that food composition may influence folate bioavailability by interfering with the intestinal deconjugation of dietary polyglutamyl folates.
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PMID:Inhibition by selected food components of human and porcine intestinal pteroylpolyglutamate hydrolase activity. 229 33

Male Wistar rats were fed for four weeks on defined diets containing no fiber additions, 10% levels of insoluble fiber derivatives (cellulose or alfalfa), or 5% levels of viscous fiber derivatives (pectin, guar gum, or metamucil). After an overnight fast, the pancreas was assayed for protein, amylase, lipase, trypsin, and chymotrypsin. Homogenates of small intestinal mucosa were analyzed for protein, alkaline phosphatase, invertase and thymidine kinase. There were, with few exceptions, no dietary effects on the exocrine pancreatic enzymes. The specific activities of the villus marker enzymes (invertase and alkaline phosphatase) tended to be higher in the proximal (but not middle or distal) intestines of the fiber-fed groups, while total activities were the same in all groups. In contrast, the activity of the crypt marker, thymidine kinase, was highest in the distal intestinal segments, and even higher in animals given the alfalfa, guar gum or metamucil-supplemented diets.
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PMID:Dietary fiber and intestinal adaptation: effects on intestinal and pancreatic digestive enzyme activities. 240 60

Core glycosylated proteins formed in the yeast endoplasmic reticulum (ER) are transported to the Golgi body, where oligosaccharides are elongated by addition of outer-chain carbohydrate. The transport process is blocked in a temperature-sensitive secretion mutant (sec18) of Saccharomyces cerevisiae, which accumulates core glycosylated invertase (product of SUC2; EC 3.2.1.26) in the ER. To approach the molecular mechanism of this transport process, we have devised a reaction in which core glycosylated invertase, accumulated in sec18 cells, is transferred to the Golgi body in vitro. For this purpose, membranes from sec18, SUC2 cells that are also defective in an outer chain alpha-1----3-mannosyltransferase (mnnl) are mixed with membranes from a strain that contains the transferase but is deficient in invertase (MNNl, delta SUC2). Transfer is detected by the acquisition of outer-chain alpha-1----3-linked mannose residues dependent on both donor and recipient membranes. The reaction is temperature and detergent sensitive and requires ATP, GDP-mannose, Mg2+, and Mn2+, and the product invertase remains associated with sedimentable membranes. Treatment of donor, but not acceptor, membranes with N-ethylmaleimide or trypsin inactivates transfer competence. These characteristics suggest that the ER, or a vesicle derived from the ER, contributes invertase to a chemically distinct compartment where mannosyl modification is executed.
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PMID:Interorganelle transfer and glycosylation of yeast invertase in vitro. 242 Dec 86

The step which requires the hydrolysis of a nucleoside triphosphate for translocation of a protein across microsome was investigated by studying translocation uncoupled from translation using two truncated products of invertase: one product contains the first 262 amino acids of the secreted invertase (Inv262); the other, the first 104 amino acids (Inv104). The truncated products were translated from RNA transcripts without a stop codon. It is demonstrated that the translated products contain an associated ribosome, and the associated ribosome is essential for the posttranslational translocation phenomenon. Also, it is demonstrated that binding of Inv262 to microsomal vesicles made from the cell wall-less mutant of Neurospora crassa does not require the hydrolysis, or the presence, of a nucleoside triphosphate. However, the posttranslational translocation across the membrane, as monitored by glycosylation of the translocated polypeptide chain, does. The data suggest that a nucleoside triphosphatase activity is associated with the translocation of invertase across the membrane. Furthermore, it is demonstrated that binding, and subsequent translocation across the membrane, is dependent on trypsin-sensitive membrane component(s).
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PMID:Translocation of a fragment of invertase across microsomal vesicles isolated from Neurospora crassa requires the hydrolysis of a nucleoside triphosphate. 297 55

Full-value diets of similar composition were given to male rats weighing 207-230 g, by intravenous (group 1) or intragastric (group 2) routes. The proportion of amino acids, fats and carbohydrates was 9.9:15.7:74.4 (with regard to their calorific value). The diet calorific value comprised 60.6 kcal/rat/day. An average mass increase in group 1 was 2.44 +/- 0.14 g/day, in group 2 - 1.75 +/- 0.11 g/day. The protein content and activities of alpha- and gamma-amylase, invertase, maltase, and glycil-L-leucine dipeptidase were assayed in the intestinal mucosa of the proximal portion of the small intestine in group 1 rats, while a decreased alpha-amylase activity in the distal portion of the small intestine was recorded in the animals of group 2. The mass of the pancreas in the rats of group 1 and 2 was authentically lower than in the control rats which received oral feeding with natural foods. The lowest mass of the pancreas was observed in the rats of group 1. Specific activity of trypsin, lipase and RNase in the pancreatic tissues of rats in groups 1 and 2 was similar. The results of the study have evidenced a lowered function of the digestive system under conditions of artificial feeding, especially in case of intravenous nutrition.
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PMID:[Digestive function of the small intestine and pancreas in rats on artificial feeding]. 309 Jul 82

There are 14 potential Asn-X-Thr/Ser glycosylation sites, or sequons, in the yeast external invertase sequence. Of these, 13 are wholly or partially glycosylated to give an average of 9-10 oligosaccharides/subunit (Reddy, V. A., Johnson, R. S., Biemann, K., Williams, R. S., Ziegler, F. D., Trimble, R. B., and Maley, F. (1988) J. Biol. Chem. 263, 6978-6985). On digestion of native holoenzyme by endo-beta-N-acetylglucosaminidase H (Endo H) an average of about seven oligosaccharides per subunit are released without affecting enzyme activity (Trimble, R. B., and Maley, F. (1977) J. Biol. Chem. 252, 4409-4412). To determine whether the remaining Endo H-resistant chains were restricted to a limited number of unique sequons or were randomly distributed on all 13, Endo H-treated native invertase was digested with either thermolysin or trypsin and the resultant glycopeptides isolated by reversed-phase high pressure liquid chromatography and gel filtration. It was found that the oligosaccharides attached to Asn92, Asn247, and Asn350 were partially resistant to Endo H, while those at Asn45 and Asn337) were completely resistant. Bio-Gel P-4 analysis revealed the Endo H-resistant oligosaccharides at Asn45, Asn92, Asn247, and Asn337 to be Man8-14GlcNAc, while the minor residual carbohydrate at Asn350 was Man greater than 50GlcNAc. The Endo H-susceptible oligosaccharides at Asn4, Asn146, and Asn256 were Man greater than 50GlcNAc while all other glycosylation sites contained Man8-14GlcNAc. Based on a hydropathic analysis of invertase, the two most Endo H-resistant oligosaccharides at Asn45 and Asn337 were located in the more hydrophobic regions of the molecule. These may form part of the folded protein structure or interacting subunit surfaces, thus restricting their accessibility to Endo H.
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PMID:Characterization of the glycosylation sites in yeast external invertase. II. Location of the endo-beta-N-acetylglucosaminidase H-resistant sequons. 313 Mar 75

Seedlings and suspension-cultured cells of carrot (Daucus carota) contain a cell wall associated as well as a soluble form of beta-fructosidase (beta F). These two forms have different pH optima: 4.6 for cell wall beta F and 5.6 for soluble beta F. Soluble beta F is relatively more abundant in the seedlings and cell wall beta F is relatively much more abundant in the cultured cells. Protoplasts of cultured cells have only the soluble form (pH optimum 5.6) indicating that the cell wall associated form is indeed extracellular in situ. Cell wall beta F was purified to homogeneity and has an Mr = 63,000. Antibodies raised against the deglycosylated enzyme cross-reacted with two soluble enzyme forms: in cultured cells, the soluble enzyme has an Mr = 58,000 and, in seedlings, there are two forms of Mr = 58,000 and 52,000. Treatment of purified cell wall beta F with endoglycosidase H and trifluoromethanesulfonic acid (complete deglycosylation) indicated that the enzyme probably has one high mannose and two complex glycans. This was confirmed by HPLC analysis of [3H]GlcNAc- and [3H]fucose-labeled glycopeptides obtained after trypsin digestion of radioactively-labeled beta F. The amino acid composition shows that cell wall beta F has 18.6% glycine.
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PMID:Characterization of beta-fructosidase, an extracellular glycoprotein of carrot cells. 314 17

Intestinal and pancreatic enzyme activities are known to respond to changes in dietary composition. Studies in rats and humans suggest that adaptive mechanisms differ between species in response to altered intakes of carbohydrate and fat. Because of increased use of the pig in the study of human nutrition, we compared the responses of pancreatic enzymes and intestinal disaccharidases in groups of 7- to 10-week-old pigs fed either high-carbohydrate/low-fat (70 cal% starch, 25% protein, 5% fat) or low-carbohydrate/high-fat (5, 25, 70%, respectively) diets for 7 and 30 days. No changes were observed in the activities for lactase, trypsin, or chymotrypsin or in the tissue protein concentrations, regardless of diet duration. High-carbohydrate/low-fat intake resulted in higher specific activities of sucrase, maltase, and amylase for both periods studied. Low-carbohydrate/high-fat intake resulted in higher specific activities of pancreatic lipase for both periods studied. The response of the intestinal disaccharidases differs from that observed previously in rodents but resembles the response reported in humans. Conversely, amylase and lipase responded similarly to the pattern in the rat. These data support the continued use of the pig as a suitable model in the study of adaptation to altered intakes of carbohydrate and fat.
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PMID:Effect of diet on intestinal and pancreatic enzyme activities in the pig. 319 78


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