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)

Yeast external invertase is a glycoprotein that exists as a dimer that can associate to form tetramers, hexamers, and octamers (Chu, F., Watorek, W., and Maley, F. (1983) Arch. Biochem. Biophys. 223, 543-555; Esmon, P. C., Esmon, B. E., Schauer, I. E., Taylor, A., and Schekman, R. (1987) J. Biol. Chem., 262, 4395-4401), a process that is facilitated by the attached oligosaccharide chains. We have studied this association by high performance liquid chromatography on a gel filtration matrix, by which procedure wild-type bakers' yeast invertase gives two peaks, and invertase from a core mutant (mnn1 mnn9) of Saccharomyces cerevisiae X2180 gives three peaks. Concentration of an invertase solution by freezing drives the dimers into higher aggregates that, at 30 degrees C, re-equilibrate to a mixture of smaller forms, the composition of which depends on pH, concentration, and time. The invertase from a mutant, mnn1 mnn9 dpg1, which underglycosylates its glycoproteins and produces invertase with 4-7 oligosaccharide chains, forms oligomers of much lower stability than the mnn1 mnn9 invertase, which has 8-11 carbohydrate chains. Both of these mutants release external invertase from the periplasm into the medium during growth, but we conclude that defects in the cell wall structure may be more important in this release than an altered tendency of the invertases to aggregate. Investigation of aggregate formation by electron microscopy revealed that all invertases, including the internal nonglycosylated enzyme, form octamers under appropriate conditions.
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PMID:Effect of glycosylation on yeast invertase oligomer stability. 354 33

Peptide N-glycosidase from Flavobacterium meningosepticum cleaves complex as well as neutral glycoproteins (Plummer, T.H., Jr., Elder, J.H., Alexander, S., Phelan, A.W., and Tarentino, A.L. (1984) J. Biol. Chem. 259, 10700-10704). Examples of neutral glycoprotein substrates include ribonuclease B (one high mannose oligosaccharide chain) and yeast external invertase (nine chains/invertase subunit). The rate of deglycosylation by the glycosidase was greatly enhanced if the glycoprotein substrate was denatured prior to enzyme treatment, from a low of 11-fold for external invertase to a high of 844-fold for ribonuclease B. Peptide N-glycosidase F was unable to cleave the asparaginyl-N-acetylglucosamine bond in endo-beta-N-acetylglucosaminidase H-modified external invertase or ribonuclease B, although that in similarly modified glycopeptide substrate was cleaved. Ribonuclease B was digested sequentially with various exoglycosidases to produce an oligosaccharide chain of varied length. Using the resulting forms of ribonuclease B as substrates for peptide N-glycosidase F, the minimum oligosaccharide chain for cleavage was the di-N-acetyl-chitobiosyl core unit.
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PMID:Requirements of cleavage of high mannose oligosaccharides in glycoproteins by peptide N-glycosidase F. 394 Oct 69

The synthesis of the glycoprotein enzymes, invertase and acid phosphatase, by protoplasts of Saccharomyces mutant 1016, is inhibited by 2-deoxy-d-glucose (2-dG) after a 20- to 30-min lag period under conditions (external sugar to 2-dG ratio of 40:1) which cause only a slight decrease in total protein synthesis. Formation of one intracellular enzyme, alpha-glucosidase, is also sensitive, but production of another, alkaline phosphatase, is unaffected. A nonmetabolized glucose analogue, 6-deoxy-d-glucose, had no inhibitory effect. The total uptake of external fructose and maltose was decreased by 2-dG after a lag period of about the same duration as that before the inhibition of synthesis of enzymes or of mannan and glucan; during this time 2-dG was taken up by the protoplasts and accumulated primarily as 2-dG-6-phosphate (2-dG-6-P). Studies in vitro showed that 2-dG-6-P inhibits both yeast phosphoglucose isomerase and phosphomannose isomerase. The intracellular levels of the 6-phosphates of glucose, fructose, and mannose did not increase in the presence of 2-dG. We suggest that the high internal level of 2-dG-6-P blocks synthesis of the cell wall polysaccharides and glycoproteins in two ways. It directly inhibits the conversion of fructose-6-P to glucose-6-P and to mannose-6-P. At the same time, it restricts the transport of fructose and maltose into the cell; however, the continuing limited uptake of the sugars still provides sufficient energy for protein synthesis. The cessation of alpha-glucosidase synthesis is probably a result of depletion of the internal pool of maltose (the inducer). Our findings support the suggestion that restriction of synthesis of the carbohydrate moiety of glycoproteins reduces formation of the active enzyme.
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PMID:Inhibition by 2-deoxy-D-glucose of synthesis of glycoprotein enzymes by protoplasts of Saccharomyces: relation to inhibition of sugar uptake and metabolism. 505 66

Rat intestinal surface-membrane glycoproteins were labelled by intraperitoneal injection of [1-(14)C]glucosamine 4h before the animals were killed. At this time, density-gradient centrifugation of disrupted brush borders indicated that glycoprotein radioactivity was distributed identically with sucrase, a plasma-membrane marker. Labelled brush borders were digested by papain for brief time-intervals known to release surface-enzyme particles without disruption of the unit membrane. Digestion for 5min released 90% of the surface sucrase, and almost one-half of the brush-border glycoprotein and label. On Sepharose 4B column chromatography most of the glycoprotein and label emerged as a single peak. This peak contained the most actively labelled glycoprotein in the brush border and was closely associated with maltase, sucrase, beta-naphthylamidase and alkaline phosphatase. The peak was partially resolved on polyacrylamide-gel electrophoresis into three bands. Each band contained a distinctive enzyme or enzyme pair, and was labelled by [1-(14)C]glucosamine. No periodic acid-Schiff-negative protein was observed in the peak material. Glycoproteins susceptible to brief digestion with papain are therefore closely linked to released surface-enzyme particles. Intestinal surface glycoproteins are heterogeneous with respect to molecular weight, electrophoretic mobility and function.
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PMID:Release of intestinal surface-membrane glycoproteins associated with enzyme activity by brief digestion with papain. 511 92

Sucrase-isomaltase (SI), an integral heterodimeric glycoprotein of the intestinal microvillus membrane, is synthesized as a single enzymically active precursor protein (pro-SI) of high relative molecular mass. After glycosylation in the Golgi complex pro-SI is transferred to the microvillus membrane where it is cleaved into the two subunits by pancreatic elastase. Pro-SI was purified by monoclonal antibody-affinity chromatography from microvillus membranes of fetal intestinal transplants in which SI is found exclusively in the non-cleaved precursor form. The N-terminal amino acid sequence of pro-SI was identical to that of the isomaltase subunit of SI which anchors the mature enzyme complex to the lipid bilayer, but it differed from the N-terminal sequence of the sucrase subunit of SI. This structural comparison indirectly gave insight into the mechanisms of membrane insertion and assembly of pro-SI during its biosynthesis. Subcellular fractionation studies indicate transient structural association of newly synthesized pro-SI with the basolateral membrane on its transfer from the Golgi complex to the microvillus membrane, suggesting that part of the basolateral membrane or its associated structures might be involved in the sorting-out processes of microvillar membrane proteins. This concept may have general relevance for the mechanisms of membrane insertion, intracellular transport and sorting of other microvillar membrane glycoproteins in the intestinal epithelial cell.
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PMID:Biosynthesis and transport of plasma membrane glycoproteins in the rat intestinal epithelial cell: studies with sucrase-isomaltase. 630 20

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

Yeast cells secrete a variety of glycosylated proteins. At least two of these proteins, invertase and acid phosphatase, fail to be secreted in a new class of mutants that are temperature-sensitive for growth. Unlike the yeast secretory mutants previously described (class A sec mutants; Novick, P., C. Field, and R. Schekman, 1980, Cell., 21:205-420), class B sec mutants (sec 53, sec 59) fail to produce active secretory enzymes at the restrictive temperature (37 degrees C). sec 53 and sec 59 appear to be defective in reactions associated with the endoplasmic reticulum. Although protein synthesis continues at a nearly normal rate for 2 h at 37 degrees C, incorporation of [3H]mannose into glycoprotein is reduced. Immunoreactive polypeptide forms of invertase accumulate within the cell which have mobilities on SDS PAGE consistent with incomplete glycosylation: sec 53 produces little or no glycosylated invertase, and sec 59 accumulates forms containing 0-3 of the 9-10 N-linked oligosaccharide chains that are normally added to the protein. In addition to secreted enzymes, maturation of the vacuolar glycoprotein carboxypeptidase Y, incorporation of the plasma membrane sulfate permease activity, and secretion of the major cell wall proteins are blocked at 37 degrees C.
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PMID:Yeast secretory mutants that block the formation of active cell surface enzymes. 636 71

N-linked oligosaccharides have been examined on glycoproteins accumulated in yeast mutants that are blocked at successive stages in the secretory pathway, and in a new mutant, gls1-1, deficient in removal of glucose from N-linked core oligosaccharides, but not blocked in secretion. Oligosaccharides on invertase, a secreted protein, and carboxypeptidase Y, a vacuolar protein, are matured normally in the gls1 mutant but retain three glucoses/carbohydrate chain. The gls1 mutation is recessive and extracts of mutant cells are inactive in release of labeled glucose from core oligosaccharides. The mutant thus lacks glucosidase I activity but could also be deficient in the other core oligosaccharide glucosidase. When transport from the endoplasmic reticulum is blocked in sec18, N-linked oligosaccharides accumulate with a size corresponding to Man8GlcNAc2 when the normal GLS1 allele is present, and Glc3Man8GlcNAc2 in the gls1 mutant. From this we infer that all glucose units are removed prior to glycoprotein transport from the endoplasmic reticulum.
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PMID:Early steps in processing of yeast glycoproteins. 638 83

Even though most of the hepatic binding capacity for mannose-terminated glycoproteins has previously been shown to reside in the hepatocytes (not in the non-parenchymal cells), detailed evidence for the specific uptake of mannose-terminated ligands has been lacking. In the present studies, yeast invertase, a large glycoprotein (Mr 270 000) containing about 50% mannose, was shown to be taken up into hepatocytes by receptor-mediated endocytosis. The uptake was saturable and could be specifically inhibited by mannosides or by a Ca2+ chelator. The asialo-glycoprotein receptor was not involved. The low-Mr (13 000) ligand ribonuclease B, which contains a single high-mannose glycan, was not taken up by hepatocytes; however, it was taken up as fast as invertase by non-parenchymal liver cells. After injection of 131I-invertase into a rat in vivo, about one-half of the labelled protein was recovered in the hepatocytes. On a per-cell basis, each endothelial cell contained 3-4 times as much radioactivity as did the hepatocytes. On fractionation of hepatocytes in sucrose gradients, invertase showed a different intracellular distribution from that of asialo-fetuin, in that invertase moved much faster into that region of the gradient where the lysosomes were recovered. This indicates that invertase and asialo-fetuin are not transported intracellularly by identical mechanisms.
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PMID:Uptake of mannose-terminated glycoproteins in isolated rat liver cells. Evidence for receptor-mediated endocytosis in hepatocytes. 649 38

The uptake and degradation of a mannose-terminated glycoprotein, yeast invertase, in char (Salmo alpinus L.) tissue was studied after intravenously injection of the 125I-labelled protein. 125I-labelled formaldehyde-treated human serum albumin (fHSA) and native HSA was also injected for comparison. Labelled invertase was rapidly cleared from blood and at about the same rate as labelled fHSA (at 8 degrees C). Approximately 50% of the initial concentration remained in blood 15 min after the injection of the ligands. Acid soluble degradation products appeared in the circulation about 60 min after the injection of the proteins. 125I-labelled invertase was recovered in the liver, pronephros and kidney. The clearance of labelled invertase from blood and the uptake in the organs were inhibited by co-injection of excess unlabelled invertase. fHSA was taken up in the pronephros and kidney tissue, while HSA was not taken up in any organs. In vitro degradation of the labelled ligands was studied in isolated pronephros cells, which had taken up the proteins in vivo. The degradation of invertase in isolated cells was partly inhibited by ammonium chloride. Ammonium chloride and chloroquine inhibited degradation of fHSA, but not leupeptin. These results together suggest that invertase and fHSA were taken up in the organs described by the receptor-mediated endocytosis. The degradation was partly or wholly lysosomal.
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PMID:Endocytosis of a mannose-terminated glycoprotein and formaldehyde-treated human serum albumin in liver and kidney cells from fish (Salmo alpinus L.). 650 Jan 36


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