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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

The denaturation of eight purified yeast enzymes, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, 3-phosphoglycerate kinase, alcohol dehydrogenase, beta-fructosidase, hexokinase and glucose-6-phosphate isomerase, promoted under controlled conditions by the free fatty acids myristic and oleic, is selective. Glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NADP+ 1 oxidoreductase, EC 1.1.1.49) is extremely sensitive to destabilization and was studied in greater detail. Results show that chain length and degree of unsaturation of fatty acids are important to their destabilizing effect, and that ligands of the enzyme can afford protection. The denaturation process results in more than one altered form. These results can be viewed in the perspective of the possibility that amphipathic substances, and in particular free fatty acids, may play a role for enzyme degradation in vivo, by initiating steps of selective denaturation.
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PMID:Selective denaturation of several yeast enzymes by free fatty acids. 35 87

Using a new selection protocol we have identified and preliminarily characterized three new loci (ADR7, ADR8 and ADR9) which affect ADH2 (alcohol dehydrogenase isozyme II) expression. Mutants were selected which activate ADH2 expression in the presence of an over-expressed, normally inactive ADR1 allele. The mutants had very similar phenotypes with the exception that one was temperature sensitive for growth. In the absence of any ADR1 allele, the mutants allowed ADH2 to partially escape glucose repression. However, unlike wildtype strains deleted for ADR1, the mutants were able to efficiently derepress ADH2. The mutations allowed a small escape from glucose repression for secreted invertase, but had no effect on the glucose repression of isocitrate lyase or malate dehydrogenase. The mutations were shown to be nonallelic to a wide variety of previously characterized mutations, including mutations that affect other glucose-repressed enzymes.
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PMID:Identification and characterization of three genes that affect expression of ADH2 in Saccharomyces cerevisiae. 142 33

mRNA steady-state levels and activities of enzymes of intermediary carbon metabolism (hexokinase, phosphoglucoisomerase, phosphofructokinase, glucose-6-phosphate dehydrogenase, phosphoglucomutase) and glucose-regulated enzymes (pyruvate decarboxylase, pyruvate dehydrogenase, invertase, alcohol dehydrogenase) were determined in glucose-limited continuous cultures of an industrial strain of Saccharomyces cerevisiae at different dilution rates (D) ranging from 0.05 to 0.315 h-1. The activity of most enzymes measured remained constant over this range except for alcohol dehydrogenase I/II which decreased proportionally with increasing dilution rate. A decrease in phosphoglucomutase activity occurred with increasing dilution rate but reached a minimum at D 0.2 h-1 and from thereon remained constant. A decrease in pyruvate decarboxylase activity and a slight decrease in phosphoglucoisomerase activity was observed. At D 0.29/0.315 h-1, at the onset of the Crabtree effect, most glycolytic enzymes remained constant except for pyruvate decarboxylase and glucose-6-phosphate dehydrogenase which increased at D 0.315 h-1 and alcohol dehydrogenase I/II which decreased. The ADHI/II and PDC1 mRNA levels obtained at the different dilution rates were in accordance with the activity measurements. The mRNA level of HXK1 decreased with increasing dilution rates, whereas the transcription of HXK2 increased. Pyruvate dehydrogenase (PDA1) and PGI1 mRNA fluctuated but no significant change could be detected. These results indicate that there is no transcriptional or translational regulation of glycolytic flux between D 0.05 h-1 and 0.315 h-1 except at the branch point between oxidative and fermentative metabolism (pyruvate decarboxylase/pyruvate dehydrogenase) at D 0.315 h-1. Surprisingly regulation of the Crabtree effect does not seem to involve transcriptional regulation of PDA1.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Analysis of transcription and translation of glycolytic enzymes in glucose-limited continuous cultures of Saccharomyces cerevisiae. 148 26

The proteins of soybean roots undergoing anaerobiosis can be grouped into three classes. Class 1 proteins are induced severalfold and at least 28 of these were identified by in vivo labeling. These proteins include the enzymes alcohol dehydrogenase (ADH), fructose aldolase, pyruvate decarboxylase, phosphoglucomutase, and lactate dehydrogenase. Class 2 proteins include such enzymes as glucose phosphate isomerase, sucrase, and malate dehydrogenase; their specific activity remains constant in aerobiosis or anaerobiosis. The third class of proteins includes those enzymes such as peroxidase whose activity decreases more than 90% after just 1 day in anaerobiosis. Immunoblotting coupled with two-dimensional chromatography of in vitro translated plant extracts demonstrated that ADH level during anaerobiosis is controlled by its mRNA concentration. Little or no mRNA for ADH was detected in aerobically grown roots. This suggests that the increased level of ADH activity is due to de novo synthesis of the mRNA rather than activation of a sequestered mRNA or superactivation of the protein.
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PMID:Gene regulation during anaerobiosis in soya roots. 262 97

The interaction of alpha-chymotrypsin, invertase, alcohol dehydrogenase and alkaline phosphatase with some ionic and non-ionic surfactants, viz. sodium dodecyl sulphate, dioctyl sodium sulphosuccinate, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and Triton X-100, has been examined by studying the effect of varying surfactant concentrations on enzyme activities as well as by determining the time-dependent inactivation and the time-independent inhibition. The kinetic parameters, Km and Vmax, for alpha-chymotrypsin-catalysed reaction in presence of sodium dodecyl sulphate were evaluated. Anionic surfactants markedly decreased enzyme activity, whereas cationic surfactants were less effective. Nonionics showed no effect. This change in enzyme activity was also dependent on the nature of enzyme.
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PMID:Stability and kinetic behaviour of some enzymes in surfactant environment. 263 63

New thermosensitive mutants of the yeast Saccharomyces cerevisiae which block the secretion of periplasmic enzymes at restriction temperature have been obtained. These mutants accumulate active low molecular weight and mature invertase species in the cell; the buoyant density of the cells in a Percoll gradient is higher than that in the wild strain cells. The mutant cells transferred to permissive temperature (25 degrees C) in the absence of protein synthesis can secrete some amount of accumulated invertase. It was found that the secretory defects of conditional mutants do not affect the activity of cytoplasmic enzymes (e.g., alcohol dehydrogenase) or the level of total protein synthesis and glycosylation and do not induce non-specific disturbances in energy metabolism and plasma membrane functions at restriction temperature. Some strains of new secretory mutants revealed uncoupled defective secretion of periplasmic enzymes and intrinsic membrane proteins (proline permease). The possibility of branching of the secretory pathway for periplasmic enzymes and cytoplasmic membrane proteins is discussed.
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PMID:[Biochemical characteristics of new thermosensitive secretory mutants of yeasts]. 332 39

Two mutants carrying different deletions of the IMP2 coding sequence of Saccharomyces cerevisiae, delta T1, which encodes a protein lacking the last 26 C-terminal amino acids, and delta T2, which completely lacks the coding region, were analysed for derepression of glucose-repressible maltose, galactose, raffinose and ethanol utilization pathways in response to glucose limitation. The role of the IMP2 gene product in the regulation of carbon catabolite repressible enzymes maltase, invertase, alcohol dehydrogenase, NAD-dependent glutamate dehydrogenase (NAD-GDH) and L-lactate:ferricytochrome-c oxidoreductase (L-LCR) was also analysed. The IMP2 gene product is required for the rapid glucose derepression of all above-mentioned carbon source utilization pathways and of all the enzymes except for L-LCR. NAD-GDH is regulated by IMP2 in the opposite way and, in fact, this enzyme was released at higher levels in both imp2 mutants than in the wild-type strain. Therefore, the product of IMP2 appears to be involved in positive and negative regulation. Both deletions result in growth and catalytic defects; in some cases partial modification of the gene product yielded more dramatic effects than its complete absence. Moreover, evidence is provided that the IMP2 gene product regulates galactose- and maltose-inducible genes at the transcriptional level and is a positive regulator of maltase, maltose permease and galactose permease gene expression.
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PMID:IMP2, a gene involved in the expression of glucose-repressible genes in Saccharomyces cerevisiae. 749 32

Conditions were optimized for rapid release and improved regeneration of protoplasts of Saccharomyces cerevisiae NCIM 3458. Rapid protoplast release was also obtained with representatives of several other yeast genera under the modified conditions of treatment. The application of the procedure in construction of a highly flocculent Saccharomyces cerevisiae with a killer character is described. Fusion was effected between UV-killed protoplasts of S. cerevisiae NCIM 3578 with a killer character and live protoplasts of the highly flocculent S. cerevisiae NCIM 3528 in the presence of polyethylene glycol (PEG) 6000. Fusants were selected using benomyl resistance as marker, the killer toxin producer rather than the highly flocculent yeast being resistant to the fungicide at a concentration of 100 micrograms ml-1. Fusants were also characterized by their DNA contents, capacity for ethanolic fermentation of molasses sugar and levels of invertase, alcohol dehydrogenase and pyruvate decarboxylase activities.
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PMID:Industrial yeast strain improvement: construction of a highly flocculent yeast with a killer character by protoplast fusion. 757 66

Glucose-repressed growth of Saccharomyces cerevisiae was analysed in a nitrogen-limited continuous culture at different dilution rates (D). The glucose consumption of the yeast decreased from 3.4 g g-1 h-1 to 3.0 g g-1 h-1 when D was decreased from 0.3 h-1 to 0.15 h-1. No transcripts of the SUC2 and HXK1 genes, encoding, respectively, invertase and hexokinase isoenzyme 1, could be detected. Because both genes are regulated by glucose repression at the transcriptional level, this confirmed that the culture was glucose repressed at every D. During the decrease in D, no change in the activities or mRNA levels of key enzymes in carbon metabolism was observed, except for alcohol dehydrogenases I and II and phosphoglucomutase. These enzymes increased in activity and/or mRNA level when D was decreased, which was also observed in glucose- and galactose-limited continuous cultures. This demonstrates that the expression levels of alcohol dehydrogenases I and II, and also phosphoglucomutase, are coupled to the growth rate of the organism. A comparison between the alcohol dehydrogenase II activity in glucose- and nitrogen-limited continuous cultures demonstrated that the growth rate contributes as much to repression of alcohol dehydrogenase II activity as does glucose. Both the glucose consumption and the activity of the glycolytic enzymes were relatively constant when D was decreased and, as a consequence, the concentrations of intracellular metabolites remained constant. A slight decrease in the glucose 6-phosphate concentration was observed, which could be caused by the slight decrease in glucose consumption at low D values.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A nitrogen-limited, glucose-repressed, continuous culture of Saccharomyces cerevisiae. 801 81


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