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)

A chemoenzymatic synthesis of homogeneous neoglycoproteins and glycopeptides was explored using oligosaccharyltransferase isolated from yeast. Neither the microsomal form nor the solubilized form of the enzyme catalyzed the transfer of the core Glc3Man9(GlcNAc)2 oligosaccharide to chemically modified ribonuclease A or alpha-lactalbumin. Similarly, no transfer was observed to the 32-amino acid peptide hormone, calcitonin, by either the membrane-bound or soluble form of oligosaccharyltransferase. However, a 17-amino acid fragment of yeast invertase with the unusual sequence containing two overlapping glycosylation sequons proved to be a good substrate, slightly less effective than the well studied tripeptide, Bz-Asn-Leu-Thr-NH2. Product analysis using gel permeation chromatography showed that the expected glycopeptides were formed and endo H-catalyzed cleavage of the oligosaccharide portion from the glycopeptides demonstrated that the glycopeptides contained the same carbohydrate moiety.
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PMID:A comparison of proteins and peptides as substrates for microsomal and solubilized oligosaccharyltransferase. 775 12

Conscious unrestrained piglets were fasted overnight and infused intravenously with [2H3]leucine for 6 h. Sucrase isomaltase and lactase phlorizin hydrolase were immunoprecipitated from jejunal mucosal membranes, and the immunoprecipitates were electrophoresed on polyacrylamide gels. Bands corresponding to the pro and mature isoforms of both enzymes were acid hydrolyzed. [2H3]leucine isotopic enrichment was measured by gas chromatography-mass spectrometry using negative chemical ionization. Plasma leucine reached isotopic steady state within 90 min. The isotopic enrichment of mucosal leucine was 73% of that of plasma leucine. The high mannose and complex glycosylated forms of prolactase were in isotopic equilibrium, and their isotopic enrichment was 94% of mucosal leucine. The fractional synthesis rates of total and membrane protein were 0.45 and 0.65 days-1, whereas the processing rates of mature lactase, sucrase, and isomaltase were 0.90, 0.23, and 0.21 days-1, respectively. Approximately 65% of the label in the sucrase isomaltase immunoprecipitate was in the complex glycosylated precursor, whereas 73% of the label in lactase phlorizin hydrolase was in the mature (160 kDa) form. We conclude that the low rate of brush-border sucrase synthesis reflects a slow rate at which the complex glycosylated precursor is processed to the brush-border form.
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PMID:Brush-border disaccharidase synthesis in infant pigs measured in vivo with [2H3]leucine. 781 Jun 60

Enzyme activities and rates of leucine and glucose uptake were measured using brush-border membrane vesicles prepared from the small intestine of 7-, 8-, 10-, and 12-week fetal (43, 49, 61, and 74% of gestation) and unsuckled, neonatal pigs. Lactase was detected in 7-week fetuses, with a large increase in activity between 10 weeks of gestation and birth. gamma-Glutamyltranspeptidase activity was stable throughout gestation, whereas sucrase activity was not detected. Active L-leucine uptake was already present at 7 weeks of gestation, with an increasing distal-to-proximal gradient observed at birth. D-glucose uptake was low at 7 weeks, but by 8 weeks it exhibited a typical overshoot phenomenon and established a decreasing proximal-to-distal gradient by 12 weeks. D-glucose uptake at all ages was directly related to incubation temperature, but less so for 7- and 10-week fetuses. By 12 weeks strict Na(+)-dependency of D-glucose uptake was observed along the entire length of the small intestine. Kinetic analysis of Na(+)-D-glucose cotransport showed a shift from the presence of both high- and low-affinity systems at 8 weeks of gestation to a single high-affinity Michaelian component at birth. In light of similarities with human fetuses, the pig may be a valuable model for studying development of intestinal transport during gestation, particularly during the final trimester, when availability of human tissue is limited.
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PMID:Intestinal brush-border membrane enzyme activities and transport functions during prenatal development of pigs. 881 24

The effect of dietary fats on the chemical composition and enzyme activities has been studied in intestinal brush border membranes (BBM) or rats. Animals were given commercial rat pellet diet (RP) or semisynthetic diet rich in either saturated [coconut oil (CCO))] or polyunsaturated [n-6, corn oil (CO) or n-3, fish oil (FO)] fat at the 10% level for 5 weeks. The membrane cholesterol/phospholipid ratio was augmented in CO- or RP-fed rats. There was an increase in level of saturated fatty acids in BBM from CCO- or FO-fed animals. n-3 polyunsaturated fatty acid content was raised in FO-fed rats, while the proportion of linoleic acid and arachidonic acid was enhanced in animals given a CO diet. Membrane fluidity was in the order of CCO < RP = CO < FO. The membrane hexose content was high (p < 0.05) in the CCO group. Hexosamines were elevated (p < 0.05) in CCO- or FO-fed rat brush borders. Membrane fucose was unaltered, while sialic acid content was elevated in CO- (p < 0.05) and FO- (p < 0.01) fed vs. CCO-fed rats. Lectin binding to brush borders corroborated these findings. The activities of alkaline phosphatase, sucrase and lactase were augmented (p < 0.001) in CCO-fed animals. Leucine-aminopeptidase and sucrase activities were depressed by FO feeding. The activities of PNP-beta-glycosidases were the highest in FO-fed rats. These results indicate that dietary fat quality markedly affects microvillus membrane lipid composition, glycosylation and enzyme functions in rat intestine.
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PMID:Dietary fat effects on brush border membrane composition and enzyme activities in rat intestine. 900 87

Glucagon-like peptide-2 (GLP-2) stimulates small intestinal growth through induction of intestinal epithelial proliferation. To examine the physiology of GLP-2-induced bowel, mice were treated with GLP-2 (2.5 micrograms) or vehicle for 10 days. Small intestinal weight increased to 136 +/- 2% of controls in GLP-2-treated mice, in parallel with 1.4 +/- 0.1- and 1.9 +/- 0.5-fold increments in duodenal RNA and protein content, respectively (P < 0.05-0.001). Similarly, the activities of duodenal maltase, sucrase, lactase, glutamyl transpeptidase, and dipeptidyl-peptidase IV (215 +/- 28% of controls; P < 0.001) were increased by GLP-2. Oral or duodenal administration of glucose or maltose did not reveal any differences in the ability of GLP-2-treated mice to absorb these nutrients, possibly because of decreases in expression of the glucose transporters sodium-dependent glucose transporter-1 (SGLT-1) and GLUT-2. In contrast, absorption of leucine plus triolein was increased after duodenal administration in GLP-2-treated mice (P < 0.01-0.001). Finally, GLP-2 did not alter other markers of intestinal or pancreatic gene expression, including levels of mRNA transcripts for ornithine decarboxylase, multidrug resistance gene, amylase, proglucagon, proinsulin, and prosomatostatin. Thus induction of intestinal growth by GLP-2 in wild-type mice results in a normal-to-increased capacity for nutrient digestion and absorption in vivo.
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PMID:Intestinal function in mice with small bowel growth induced by glucagon-like peptide-2. 922 51

To examine the possibility of active recycling of Emp24p between the endoplasmic reticulum (ER) and the Golgi, we sought to identify transport signal(s) in the carboxyl-terminal region of Emp24p. Reporter molecules were constructed by replacing parts of a control invertase-Wbp1p chimera with those of Emp24p, and their transport rates were assessed. The transport of the reporter was found to be accelerated by the presence of the cytoplasmic domain of Emp24p. Mutational analyses revealed that the two carboxyl-terminal residues, leucine and valine (LV), were necessary and sufficient to accelerate the transport. The acceleration was sequence specific, and the terminal valine appeared to be more important. The LV residues accelerated not only the overall transport to the vacuole but also the ER to cis-Golgi transport, suggesting its function in the ER export. Hence the LV residues are a novel anterograde transport signal. The double-phenylalanine residues did not affect the transport by itself but attenuated the effect of the anterograde transport signal. On the other hand, the transmembrane domain significantly slowed down the ER to cis-Golgi transport and effectively counteracted the anterograde transport signal at this step. It may also take part in the retrieval of the protein, because the overall transport to the vacuole was more evidently slowed down. Consistently, the mutation of a conserved glutamine residue in the transmembrane domain further slowed down the transport in a step after arriving at the cis-Golgi. Taken together, the existence of the anterograde transport signal and the elements that regulate its function support the active recycling of Emp24p.
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PMID:Identification of potential regulatory elements for the transport of Emp24p. 984 83

To get high level secretion of human lysozyme in Pichia pastoris, the following three signal sequences and one prepro sequence were evaluated: chicken lysozyme signal peptide, leucine-rich artificial signal peptide, Saccharomyces invertase signal peptide, and Saccharomyces prepro sequence of alpha factor (MF-alpha Prepro). Transformants harboring a lysozyme gene with MF-alpha Prepro secreted 20-fold more lysozyme than those harboring the lysozyme gene with any one of the other three signal sequences. Three mutant leader sequences derived from MF-alpha Prepro were constructed to discover the function of the pro region. The secretion was dramatically decreased by eliminating the pro region of MF-alpha Prepro. In contrast, MF-alpha Prepro with the EAEAEA sequence directed the secretion of an equivalent level of lysozyme having the extra amino acids (EAEAEA) in its N-terminus. For the effective secretion of native human lysozyme, MF-alpha Prepro without any spacer sequences was most suitable. The secreted protein by MF-alpha Prepro construct was identical with the authentic human lysozyme, judging from N-terminal amino acid sequencing and molecular mass spectrometric and crystallographic analysis.
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PMID:Human lysozyme secretion increased by alpha-factor pro-sequence in Pichia pastoris. 1063 62

We report here on the molecular nature of an EMS-induced mutant, mn1-89, a leaky semidominant allele of the Miniature1 (Mn1) seed locus that encodes a seed-specific cell wall invertase, INCW2. The mn1-89 locus specifies normal levels of the Incw2 transcript but extremely low levels (about 6% of normal) of the protein and enzyme activity are expressed. Sequence analysis of Incw2 clones derived from the parental Mn1 and the mutant genotypes shows a C to T transition in the mn1-89 allele, leading to a single amino acid alteration (proline to leucine) near the C-terminus of the mutant INCW2 protein. Although this change is not in the catalytic domain, putative N-glycosylation sites, or the beta-fructosidase motif, it does lie in a motif that is well conserved among all plant invertases and related fructosyltransferases. On the basis of these genetic in planta data, we believe we have identified a proline residue in a hitherto unknown GPFG motif as critical for the stability of such proteins. The single base change (C to T) also leads to the elimination of a BglI restriction site in the mutant allele. Indeed, BglI restriction digests of genomic DNAs from mn1-89 and Mn1 genotypes show one and two fragments, respectively. Sequence analysis of RT-PCR-derived endosperm Incw clones from mn1-1 (the reference allele) seeds predict five amino acid substitutions relative to Mn1. Whether or not these sequences are encoded by the mn1-1 locus or another non-allelic Incw gene in the maize genome remains to be elucidated.
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PMID:A point mutation at the Miniature1 seed locus reduces levels of the encoded protein, but not its mRNA, in maize. 1077 57

Congenital sucrase-isomaltase deficiency (CSID) is an autosomal recessive human intestinal disorder that is clinically characterized by fermentative diarrhea, abdominal pain, and cramps upon ingestion of sugar. The symptoms are the consequence of absent or drastically reduced enzymatic activities of sucrase and isomaltase, the components of the intestinal integral membrane glycoprotein sucrase-isomaltase (SI). Several known phenotypes of CSID result from an altered posttranslational processing of SI. We describe here a novel CSID phenotype, in which pro-SI undergoes an unusual intracellular cleavage that eliminates its transmembrane domain. Biosynthesis of pro-SI in intestinal explants and in cells transfected with the SI cDNA of this phenotype demonstrated a cleavage occurring within the endoplasmic reticulum due to a point mutation that converts a leucine to proline at residue 340 of isomaltase. Cleaved pro-SI is transported to and processed in the Golgi apparatus and is ultimately secreted into the exterior milieu as an active enzyme. To our knowledge this is the first report of a disorder whose pathogenesis results not from protein malfolding or mistargeting, but from the conversion of an integral membrane glycoprotein into a secreted species that is lost from the cell surface.
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PMID:Congenital sucrase-isomaltase deficiency arising from cleavage and secretion of a mutant form of the enzyme. 1090 44

The present study examines the effects of severe stress on digestive and resorptive functions of the small intestine. Transverse 20-minute acceleration (+10 Gx) results in an increase of invertase activity, particularly in distal parts of the small intestine. Although the activity of glycyl-l-leucine dipeptidase was changed, the fluctuations were less pronounced than those in invertase activity. Acceleration also produces rise in glucose accumulated in the intestinal mucosa and intensification of active carbohydrate transport. The displacement of the proximodistal gradient of invertase activity and carbohydrate resorption was significant. Dipeptidase and invertase activities in intestinal sacs and in tissue homogenates were depressed following exposure to 15-, 30- and 60-day hypokinetics. In distal parts the invertase activity was increased, and the resorptive function was enhanced. Following exposure to unusual gaseous atmospheres (hypoxic, hypercapnic and hyperoxic) there was an increase in active glucose transport over the entire length of the small intestine. Heat produces a decrease in invertase activity both in intact cells and homogenates. There were no pronounced changes in dipeptidase activity. Transport processes exhibited some variations.
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PMID:Digestive and resorptive function of the small intestine in stressful situation. 1269 Nov 11


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