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 mutants with glucose-insensitive formation of mitochondrial enzymes were isolated starting with a strain completely lacking alcohol dehydrogenase activity. The mutations could uniquely be attributed to a single nuclear gene, designated CCR80. They were largely dominant. Glucose-resistant enzyme formation was most prominent with regard to mitochondrial enzymes succinate dehydrogenase and NADH: cytochrome c oxidoreductase. The effect of CCR80r mutations was rather small but significant on the gluconeogenetic enzymes isocitrate lyase, malate synthase and fructose-1,6-bisphosphatase and on invertase synthesis. The repressive effect of maltose in CCR80r mutants was also reduced showing that glucose-resistance is not caused by a mere hexose uptake defect. This regulatory disorders were not accompanied by reduced levels of glycolytic enzymes or drastically altered levels of glycolytic intermediates. Aerobic fermentation of glucose was almost completely inhibited in the mutants; anaerobic glucose degradation was reduced but not completely abolished. Therefore, the mutants appear to be altered in the regulation of glycolysis. A largely glucose-resistant synthesis of respiratory enzymes is obviously a corollary of this alteration.
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PMID:A yeast mutant with glucose-resistant formation of mitochondrial enzymes. 20 62

Saccharomyces cerevisiae -136ts synthesized invertase in media containing maltose and sucrose. In the presence of glucose synthesis of enzyme took place when the sugar concentration was lower than 1%. At higher concentrations enzyme formation was repressed. Analysis of the glucose effect before RNA inhibition showed that the hexose interfered with the transcription of DNA into invertase messenger RNA. Translation of invertase messenger already formed was also inhibited and the kinetics of this effect was similar to that produced by cycloheximide. Invertase activity was independent of glucose suggesting that the hexose produces no catabolite inhibition of invertase activity. Inhibition of invertase translation by glucose turned out to be reversible but the amount of enzyme produced was dependent on duration of treatment. It is suggested that the catabolite repression of invertase synthesis produced by glucose operates at the levels of transcription and translation and produces an increase in the rate of mRNA degradation. The catabolite repression has no effect on secretion and does not interfere with the catalytic activity of invertase.
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PMID:The mechanism of catabolite inhibition of invertase by glucose in Saccharomyces cerevisiae. 32 Oct 21

The mechanism of inhibition by 2-deoxy-D-glucose of the synthesis of yeast wall polysaccharides and glycoproteins was investigated in Saccharomyces cerevisiae cells and protoplasts. The extent of the inhibition of mannan and glucan synthesis was found to be dependent on whether glucose or mannose was used as the carbon source in the medium. During growth on glucose, 2-deoxy-D-glucose inhibited more intensively mannan than glucan formation. Biosynthesis of wall glucan was strongly suppressed in mannose medium. Selective incorporation of 2-deoxy-D-glucose occurred into that polysaccharide, synthesis of which was more inhibited under given conditions. Suggestive evidence has been obtained that the decisive factor for the proportion of glucan and mannan in the walls is the direction of glucose 6-phosphate/mannose 6-phosphate interconversion dependent on the exogeneous hexose. No close correlation was found between the inhibition of mannan synthesis and the appearance of the mannan-protein enzymes invertase and acid phosphatase. Effect of 2-deoxy-D-glucose was therefore investigated on the parallel synthesis of protein, mannan and several extracellular and intracellular enzymes in protoplasts grown on glucose and mannose. The results obtained pointed out that the hindrance of the secretion of mannan-protein enzymes is of a complex nature and related more to the inhibition of synthesis of the protein moiety than to the inhibition of glycosylation. Synthesis of several enzymes was found to be a subject of a metabolic control by 2-deoxy-D-glucose or its metabolites.
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PMID:Mechanism of 2-deoxy-D-glucose inhibition of cell-wall polysaccharide and glycoprotein biosyntheses in Saccharomyces cerevisiae. 110 Mar 78

Ethanol feeding to rats for 40 days enhanced (p < 0.001) the activities of alkaline phosphatase, sucrase, gamma-glutamyltransferase (GTP), and p-nitrophenyl (PNP)-beta-D-galactosidase (p < 0.05) with no change in leucine amino peptidase (LAP) and PNP-beta-D-glucosidase activities in intestine compared with control rats. The activities of alkaline phosphatase, sucrase, and GTP were diminished (p < 0.01) in ethanol-fed malnourished rats. There was no change in LAP activity, but the levels of glucosidase and galactosidase were elevated under these conditions. Brush-border sialic acid, fucose, hexose, and hexosamine contents were elevated in ethanol-fed protein-deficient animals. Ethanol administration to normally fed rats elevated the membrane sialic acid and hexose contents, reduced fucose content, and had no effect on brush-border hexosamine content compared with the control group. These results are in agreement with data on lectin binding to brush borders under these conditions. Alcohol ingestion reduced the incorporation of [14C]-glucosamine into brush borders in rats maintained on an 18% protein diet but augmented the incorporation of [14C]-glucosamine and [14C]-mannose in protein-malnourished membranes. These observations suggest that nutrition status influences the sensitivity of microvillus membrane glycosylation to ethanol feeding in rat intestine.
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PMID:Chronic ethanol feeding and microvillus membrane glycosylation in normal and protein-malnourished rat intestine. 142 85

The effect of total parenteral nutrition on nutrients absorption and glycoprotein changes of brush border membrane was examined in rat small intestine. In total parenteral nutrition rats, a marked decrease in activity of brush border enzymes was observed mainly in the proximal and middle segments of the intestine. Galactose perfusion of jejunal segment showed that hexose absorption was significantly inhibited, while intestinal absorption of glycine or dipeptide, glycylglycine was not significantly affected by total parenteral nutrition treatment. When brush border membrane glycoprotein profile was examined by [3H]-glucosamine or [3H]-fucose incorporation into jejunal loops, significant changes were observed in the glycoprotein pattern of brush border membrane especially in the high molecular weight range over 120 kDa after total parenteral nutrition treatment, suggesting strong dependency of glycoprotein synthesis on luminal substances. Molecular weight of sucrase isomaltase in brush border membrane detected by specific antibody showed no significant difference, however, in total parenteral nutrition and control rats. Also, molecular weight of specific sodium glucose cotransporter of intestinal brush border membrane detected by selective photoaffinity labelling was not altered in total parenteral nutrition rats. It may be that prolonged absence of oral food intake may produce significant biochemical changes in brush border membrane glycoprotein and absorptive capacity of small intestine, but these changes were not observed in all brush border membrane glycoproteins.
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PMID:Changes in intestinal absorption of nutrients and brush border glycoproteins after total parenteral nutrition in rats. 158 92

The common hookworm (Ancylostoma ceylanicum) infection of humans was studied in golden hamsters model system. Significant biochemical modulations were observed in hamster jejunal brush border membrane (BBM), the primary site of infection. Analysis of BBM at the peak of infection (3-weeks) revealed a marked decrease in the activities of sucrase, lactase and maltase, while activities of alkaline phosphatase, (Ca2+ + Mg2+)-ATPase and gamma-glutamyl transpeptidase were increased. Kinetic studies conducted with maltase, a superficially localised enzyme of jejunal BBM, revealed loss of enzyme active site during the infection. Among other constituents, the levels of cholesterol and triglycerides were significantly decreased with slight increase in phospholipid content in the infected animals. The hookworm infection also caused a decline in total hexose content indicating an altered membrane glycocalyx. Conversely, there was significant enhancement of hydroxyproline and sialic acid contents. SDS-PAGE analysis showed an enhancement in both low and high molecular weight proteins in jejunal BBM preparations of the infected group. Gel electrophoresis of glycoproteins further revealed the appearance of two additional peaks in the low molecular weight region and concomitant disappearance of a peak in the high molecular weight region. These results strongly support the view that the hookworm infection causes severe damage not to the site of attachment alone but also to the entire cell lining of the jejunum and therefore could influence overall digestion and absorption.
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PMID:Biochemical analysis of jejunal brush border membrane of golden hamster: pathogenic modulations due to ancylostomiasis. 159 19

A rapid, enzyme-linked colorimetric assay, for the sequential determination of nanomole quantities of glucose and fructose in the same sample, has been developed for the measurement of fructosyl transferase activity in plant extracts. The assay extends the conventional dehydrogenase-linked assay for these sugars by utilizing the intermediary electron carrier, phenazine methosulfate, to couple NADP reduction to the production of a formazan dye from the tetrazolium salt, thiazolyl blue, in a form suitable for measurement using a microtiter plate reader. When the microtiter plate assay was used to measure the activities of yeast invertase and sucrose:sucrose fructosyl transferase from Lolium temulentum, results obtained were very similar to results obtained using the conventional procedure. The rapidity, small scale, and ease of execution of the method offers considerable advantages over the conventional hexose assay and is particularly suitable for screening of large numbers of small samples, exploiting both the speed of the microtiter plate reader and the facility of for microcomputer processing of data. The potential of this method for use with other enzyme systems and other metabolites is discussed.
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PMID:Colorimetric microtiter plate assay of glucose and fructose by enzyme-linked formazan production: applicability to the measurement of fructosyl transferase activity in higher plants. 344 22

When S. cerevisiae growing in the presence of glucose (repressive condition) was shifted to higher temperatures, invertase was secreted. This secretion required protein synthesis, but was independent of RNA formation (Mormeneo & Sentandreu 1982). In addition accumulation of invertasespecific messenger RNA occurred in the absence of protein synthesis but was expressed only after synthesis of protein. Invertase mRNA was continuously synthesized under repressive conditions and the levels of this mRNA were regulated by the presence of glucose. The hexose regulated the concentration of this mRNA at the level of transcription and/or by sensitization of this messenger RNA. The expression of the invertase mRNA present in the cells under repressive conditions was also regulated by glucose at the level of translation and/or secretion. As a result of these processes, under repressive conditions invertase is eliminated before secretion takes place.
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PMID:Molecular events associated with glucose repression of invertase in Saccharomyces cerevisiae. 352 42

Production of invertase by many strains of yeast is repressed in the presence of hexoses. This phenomenon interferes with studies on the secretion of invertase and with the preparation of large quantities of the enzyme for examination of its chemical and physical characteristics. Saccharomyces strain 303-67, a diploid carrying the single gene SUC-2 for (hexose repressible) invertase production, was subjected to ultraviolet irradiation. No single-step mutations to high level resistance were detected. By a two-step irradiation process mutants were obtained with differing degrees of resistance. The biochemical and genetic characteristics of these mutants are summarized with particular emphasis on FH4C (the most resistant). Although the steady state level of cyclic 3', 5'-adenosine monophosphate (cyclic AMP) was usually slightly higher in cells grown in low- rather than in high-glucose media, the level of cyclic AMP was not correlated with the sensitivity of invertase synthesis to glucose repression. In mutant FH4C, 1 to 2% of the total cell protein is present as invertase; synthesis of alpha-glucosidase is also resistant to repression by hexoses. This mutant does not sporulate and is probably a haploid of a-mating type with low frequency of conjugation and poor viability of conjugants. Mutants 1016 and 1710 are substantially resistant to hexose repression and still sporulate well. They may be useful for genetic analysis of hexose resistance.
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PMID:Saccharomyces mutants with invertase formation resistant to repression by hexoses. 434 29

1. An account is given of the absorption of disaccharides by the small intestine of Rana temporaria, R. pipiens and Bufo vulgaris perfused in vitro through the vascular system. Maltase and trehalase activity are found in the intestine of all three species; very small amounts of sucrase are present in the intestine of R. pipiens but there is no evidence for the presence of lactase in any of the animals studied.2. During maltose absorption free glucose appears in the vascular effluent and in the intestinal lumen. Only very small quantities of disaccharide are found in the vascular effluent. The concentration of free glucose in the intestinal lumen during maltose absorption is not high enough to account for the rates of glucose transport observed. The rate of appearance of glucose in the vascular effluent is determined by the concentration of disaccharide in the luminal fluid, and hexose, free in solution in the lumen, is not an obligatory intermediate in the process of disaccharide absorption.3. For R. pipiens more than 90% of the maltase activity in the system is present in the intestinal wall and the rate of maltose hydrolysis by maltase, free in the intestinal lumen, is found to be inadequate to account for the rates of appearance of glucose observed to occur in the lumen and in the vascular effluent. It is not possible to wash away maltase activity from the intestinal wall.4. The kinetic properties of maltase and trehalase acting in situ are of the Michaelis-Menten type; the apparent K(m) is 2 mM for maltase, and 3 mM for trehalase.5. The relationship which exists between the rate of absorption of glucose and the concentration in the luminal fluid of either disaccharide or free glucose is of the Michaelis-Menten type. Expressed in molar units, the apparent K(m) for the glucose transport is about one fifth that of the disaccharidase. The maximum rate of glucose transport observed is less than the maximum rate of disaccharide hydrolysis. In R. pipiens equimolar concentrations in the intestinal lumen of the monomer free glucose, or of the dimer, maltose, yield approximately equal rates of transport of the free hexose.6. It is concluded that in the amphibian, either intestine disaccharide hydrolysis and glucose transport are functions of separate subcellular systems which spatially are very closely related, or that the hydrolysis and transport are different facets of the activity of a common system.
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PMID:Disaccharide absorption by amphibian small intestine in vitro. 568 31


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