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)

The coding sequence of the SUC2 locus was placed under the control of the constitutive ADH1 promoter and transcription terminator in a centromere-based yeast plasmid vector from which invertase is expressed in a Suc- strain of Saccharomyces cerevisiae. Mutants in the signal peptide sequence were produced by replacing this region of the gene with synthetic oligonucleotide cassettes containing mixtures of nucleotides at several positions. The mutants could be divided into three classes on the basis of the ability to secrete invertase. Class I mutants produced secreted invertase but in reduced amount. The class II mutant, 4-55B, also exhibited reduced a level of invertase, but a significant fraction of the enzyme was intracellular. Class III mutants were partially defective in translocation from the cytoplasm to the endoplasmic reticulum and produced enzymatically active, unglycosylated preinvertase in the cytoplasm. Class III mutant preinvertases were also defective in translocation across canine pancreas microsomes. These results suggested that the reduced level of invertase resulted from proteolytic degradation of inefficiently transported intermediates. Comparison of the sequences of the mutant signal peptides indicated that amino acids at the extreme amino terminus and adjacent to the cleavage site play a crucial role in the secretory process when combined with a mutation within the hydrophobic core.
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PMID:Cassette mutagenic analysis of the yeast invertase signal peptide: effects on protein translocation. 267 71

The effect of peptic-tryptic digested gliadin (PT-gliadin) on the increase in sucrase activity in different fractions of tissue cultured fetal chick duodenum was investigated and compared with that of monensin, a known perturbant of the Golgi complex. PT-gliadin diminished the rise in sucrase activity in the tissue homogenate, in a brush border fraction, and in the high speed supernatant, whereas the activity in a Ca2+-pelleted fraction including endoplasmic reticulum and Golgi apparatus was unaffected. In contrast, monensin caused a proportional inhibition of the increase in sucrase activity in all fractions examined. The findings might suggest that PT-gliadin is able to affect intracellular processing of sucrase with the site of attack being distal to that of monensin in the biogenesis of the enzyme. Whether the effect of PT-gliadin on fetal gut is relevant also for celiac intestine remains to be established.
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PMID:Effect of gliadin on the distribution of sucrase among different fractions of fetal chick intestine. 277 45

Immunoelectron microscopy of Saccharomyces cerevisiae cells embedded in Lowicryl K4M has been used to localize invertase and plasma membrane (PM) ATPase in secretory organelles. sec mutant cells incubated at 37 degrees C were prepared for electron microscopy, and thin sections were incubated with polyclonal antibodies, followed by decoration with protein A-gold. Specific labeling of invertase was seen in the lumen of the endoplasmic reticulum, Golgi apparatus, and secretory vesicles in mutant cells that exaggerate these organelles. PM ATPase accumulated within the same organelles. Double-immune labeling revealed that invertase and PM ATPase colocalized in secretory vesicles. These results strengthen the view that secretion and plasma membrane assembly are biosynthetically coupled in yeast.
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PMID:Coincident localization of secretory and plasma membrane proteins in organelles of the yeast secretory pathway. 296 84

The intestinal microvilli of fetal origin in human amniotic fluid were purified by Ca2+ precipitation of contaminating organelles followed by differential centrifugation of microvillar membranes. In the purified preparation, the specific activity of the microvillar marker-enzymes maltase and sucrase increased about 77-fold over that in cell-free amniotic fluid. Significant contamination of the purified preparation by endoplasmic reticulum (microsomes) and lysosomes was ruled out on the basis of a low content of the marker enzymes glucose-6-phosphatase (microsomes) and acid phosphatase (lysosomes). Amniotic fluid microvilli contain typical enzymes of the fetal intestine including maltase, sucrase, trehalase, alkaline phosphatase and gamma-glutamyltransferase, and their morphology by electron microscopy resembles that of vesiculated intestinal microvilli. Prenatal detection of genetic diseases due to a deficiency of a protein expressed in these membranes or associated to abnormal microvilli seems feasible.
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PMID:Fetal intestinal microvilli in human amniotic fluid. 302 83

Yeast invertase forms a homo-octamer of core glycosylated subunits during assembly in the lumen of the endoplasmic reticulum. This form has been purified from mutant cells (sec18) in which transport of secreted proteins from the endoplasmic reticulum is blocked. No heterologous protein subunits are found in the purified material. Analysis of invertase derived from wild type cells or from mutant cells blocked at subsequent stages in secretion demonstrates that invertase remains a homo-octamer throughout the pathway even though the extent of subunit glycosylation increases. Purified octameric invertase is dissociated into dimer units that reassociate in the presence of polyethylene glycol. Negatively stained preparations show the dissociated enzyme as individual spheres, whereas octameric invertase appears as four associated spheres. Assembly of the octamer in vitro and in vivo is facilitated by the presence of N-linked carbohydrate. Selective release of dimeric glycosylated invertase from intact yeast cells suggests that oligomerization helps retain the enzyme in the periplasmic space.
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PMID:Structure, assembly, and secretion of octameric invertase. 303 Oct 75

In mammalian cells intracellular transport is inhibited during mitosis. Here we show that in the yeast Saccharomyces cerevisiae secretion continues uninterrupted during mitosis. S. cerevisiae cells were arrested in mitosis by treating wild-type cells with the microtubule-inhibitor nocodazole, or by incubating a temperature-sensitive cell division cycle mutant (cdc16) at the restrictive temperature. Secretion of invertase into the periplasmic space was equally efficient in mitotic and in unsynchronized cells. Electron microscopy of nocodazole-treated mitotic wild-type cells revealed stretches of rough endoplasmic reticulum, strongly fenestrated Golgi cisternae and clusters of vesicles with the diameter of 30-90 nm. Secretion of invertase was inhibited in mitotic sec7 cells at the restrictive temperature, but continued at the permissive temperature. Sec7 is a mutant strain where intracellular traffic is blocked in unsynchronized cells in the Golgi complex at the restrictive temperature. Thus, the elements of the mitotic Golgi complex appear to be able to support intracellular traffic.
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PMID:Secretion of invertase in mitotic yeast cells. 304 81

In animal cells, luminal endoplasmic reticulum (ER) proteins are prevented from being secreted by a sorting system that recognizes the C-terminal sequence KDEL. We show that yeast has a similar sorting system, but it recognizes HDEL, rather than KDEL: derivatives of the enzyme invertase that bear the HDEL signal fail to be secreted. An invertase fusion protein that is retained in the cells is partially modified by outer-chain mannosyl transferases, which reside in the Golgi element. This supports the view, based on studies in animal cells, that ER targeting is achieved by continuous retrieval of proteins from the Golgi. We have used an invertase fusion gene to screen for mutants that are defective in this sorting system. Over 60 mutants were obtained; eight of these are alleles of a single gene, erd1. The mutant strains grow normally at 30 degrees C, but instead of retaining the fusion protein in the cells, they secrete it.
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PMID:Sorting of soluble ER proteins in yeast. 304 74

Saccharomyces cerevisiae HMSF-176 (sec 18), a thermosensitive secretory mutant blocked at the endoplasmic reticulum (ER) level, drastically increased its osmotic sensitivity when grown at the restrictive temperature of 37 degrees C in high glucose concentration. This fact led to the erroneous interpretation that glucanases were inactive when localized in the ER. The development of a suitable osmotic stabilizer now indicates that sec 18 accumulates exoglucanase activity. Another ER-blocked mutant behaved in a similar way. All the accumulated exoglucanase was found in a soluble form. By contrast, a significant portion of the accumulated invertase remained in a membrane-bound form.
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PMID:Accumulation of exoglucanase activity in yeast secretory mutants blocked at the endoplasmic reticulum level. 308 68

Representative conditional yeast secretory mutants, blocked in transport of secretory and plasma membrane proteins from the endoplasmic reticulum (sec 18), from the Golgi body (sec 7) and in transport of secretory vesicles (sec 1), accumulated exoglucanase, a constitutive yeast activity, when incubated at the restrictive temperature (37 degrees C). Different proportions of the accumulated activity were released by mutant cells under permissive conditions. The presence or absence of cycloheximide during the secretion period made no differences in the results. More than 90% of the internal activity was bound to membrane in wild type cells. However, only the soluble pool underwent changes during the accumulation or secretion periods. The bulk of secretory invertase accumulated by sec 1 was also soluble. By contrast sec 7 and sec 18 accumulated membrane-bound as well as soluble invertase forms and both were secreted in similar proportions in each mutant. More than 90% of the accumulated invertase was secreted at the permissive temperature in sec 18 cells. That percentage was significantly lower for exoglucanase (less than 65%). Concomitantly, invertase accumulated by this mutant exited from the cells with a lower half time (t1/2 = 24 min) than accumulated exoglucanase (t1/2 = 150 min). These results may be interpreted assuming that exoglucanase is exported by a passive flow of the soluble pool.
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PMID:Accumulation and secretion of exoglucanase activity in yeast secretory mutants. 310 78

A set of protein hybrids composed of variable portions of the amino-terminal residues of the yeast phosphate-repressible acid phosphatase (product of PHO5) and an active fragment of bacterial beta-galactosidase has been constructed. When these PHO5-LACZ hybrids are expressed in a yeast strain carrying an intact chromosomal PHO5 gene, they show a size-dependent interference with the secretion of native acid phosphatase. Hybrid proteins containing approximately 50 residues of acid phosphatase do not affect secretion of native acid phosphatase. Hybrids containing greater than 200 residues of acid phosphatase reduce the amount of secreted acid phosphatase more than by 50%. The interference with secretion is specific for acid phosphatase. The hybrids do not affect secretion of invertase, and do not confer a growth-deficient phenotype on yeast. Both the hybrid proteins and acid phosphatase accumulate in non-glycosylated, membrane-bound forms which are sensitive to proteolysis from the cytoplasmic side of the membrane. The hybrids and accumulated acid phosphatase co-migrate on Percoll density gradients with markers of the endoplasmic reticulum, but not with markers of the Golgi or secretory vesicles. These results suggest that PHO5-LACZ hybrid proteins specifically block secretion of native acid phosphatase by interfering with enzyme after targeting but before translocation across the endoplasmic reticulum.
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PMID:PHO5-LACZ hybrid proteins block translocation of native acid phosphatase in Saccharomyces cerevisiae. 312 33


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