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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 new mutation has been described which confers resistance to catabolite repression in Saccharomyces cerevisiae. The mutant allele, termed grr-1 for glucose repression-resistant, is characterized by insensitivity to glucose repression for the cytoplasmic enzymes invertase, maltase, and galactokinase, as well as the mitochondrial enzyme cytochrome c oxidase. Hexokinase levels in grr-1 mutants are approximately 3-fold higher than the corresponding activity of the parental strain. Although the grr-1 allele is expressed phenotypically similarly to the hex-1 (hxk-2) and hex-2 mutations described by Entian et al. (1977) and Zimmermann and Scheel (1977) respectively, we have shown genetically and physiologically that grr-1 represents a new class of mutation.
Mol Gen Genet 1984
PMID:Isolation and characterization of a pleiotropic glucose repression resistant mutant of Saccharomyces cerevisiae. 632 21

A sample of human dental plaque was homogenized in transport fluid and inoculated simultaneously into a glucose-limited and a glucose-excess chemostat maintained at pH 7.0 and a dilution rate (D) of 0.05 h-1. In an attempt to ensure the establishment of slow-growing bacterial populations, two further inoculations of each chemostat with fresh samples of dental plaque took place before a steady-state was attained at this dilution rate. The dilution rate was increased step-wise to D = 0.6 h-1, and then returned directly to D = 0.05 h-1. Contrary to chemostat theory, microbial communities with a high species diversity were maintained under all of the experimental conditions employed, although not all of the bacterial populations present in the inocula established successfully in the chemostat. At each steady-state the bacteriological composition and biochemical properties (fermentation products, enzyme assays and acid production) of the communities of each chemostat was determined. Higher cell yields and a slightly more diverse community were obtained from the glucose-limited chemostat at all dilution rates. A complex mixture of end products of metabolism was obtained from the glucose-limited chemostat, suggesting amino acid catabolism, while lactate was the predominant acid of the glucose-excess culture. In washed-cell experiments, communities from the glucose-excess chemostat produced the lower terminal pH values following a pulse of glucose, with the lowest pH values occurring at the higher dilution rates. A film of micro-organisms, which accumulated around the neck of the chemostat, was sampled at the end of the experiment. The microbial composition of the films from each chemostat differed markedly, and both were different to the community of the bulk fluid of the respective chemostat. Spirochaetes and a population of yeasts were detected in the films from the glucose-limited and glucose-excess chemostats, respectively. No invertase or glucosyltransferase activity, and little glucoamylase-specific glycogen was detected in the communities from either chemostat, although significant endogenous activity, particularly at high dilution rates, was obtained with washed-cells from the glucose-excess chemostat. The results suggest that the chemostat could make a valuable contribution to the study of the ecology of dental plaque.
J Gen Microbiol 1983 Mar
PMID:The influence of growth rate and nutrient limitation on the microbial composition and biochemical properties of a mixed culture of oral bacteria grown in a chemostat. 634 8

A selection system has been devised for isolating hexokinase PII structural gene mutants that cause defects in carbon catabolite repression, but retain normal catalytic activity. We used diploid parental strains with homozygotic defects in the hexokinase PI structural gene and with only one functional hexokinase PII allele. Of 3,000 colonies tested, 35 mutants (hex1r) did not repress the synthesis of invertase, maltase, malate dehydrogenase, and respiratory enzymes. These mutants had additional hexokinase PII activity. In contrast to hex1 mutants (Entian et al., Mol. Gen. Genet. 156:99-105, 1977; F.K. Zimmermann and I. Scheel, Mol. Gen. Genet. 154:75-82, 1977), which were allelic to structural gene mutants of hexokinase PII and had no catalytic activity (K.-D. Entian, Mol. Gen. Gent. 178:633-637, 1980), the hex1r mutants sporulated hardly at all or formed aberrant cells. Those ascospores obtained were mostly inviable. As the few viable hex1r segregants were sterile, triploid cells were constructed to demonstrate allelism between hex1r mutants and hexokinase PII structural gene mutants. Metabolite concentrations, growth rate, and ethanol production were the same in hex1r mutants and their corresponding wild-type strains. Recombination of hexokinase and glucokinase alleles gave strains with different specific activities. The defect in carbon catabolite repression was strongly associated with the defect in hexokinase PII and was independent of the glucose phosphorylating capacity. Hence, a secondary effect caused by reduced hexose phosphorylation was not responsible for the repression defect in hex1 mutants. These results, and those with the hex1r mutants isolated, strongly supported our earlier hypothesis that hexokinase PII is a bifunctional enzyme with (i) catalytic activity and (ii) a regulatory component triggering carbon catabolite repression (Entian, Mol. Gen. Genet. 178:633-637, 1980; K.-D. Entian and D. Mecke, J. Biol. Chem. 257:870-874, 1982).
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PMID:Saccharomyces cerevisiae mutants provide evidence of hexokinase PII as a bifunctional enzyme with catalytic and regulatory domains for triggering carbon catabolite repression. 637 Sep 59

Various amino acid insertions have been introduced into the proximal portion of the signal sequence of secreted yeast invertase. The altered invertase genes have been reintroduced into yeast and monitored for their ability to direct synthesis of secreted invertase in vivo. The insertions should alter the signal polypeptide local secondary structure as predicted by the Chou and Fasman rules (1978). Secretion of these altered invertase polypeptides is not blocked by the amino acid insertions.
Mol Gen Genet 1984
PMID:Conformational alterations in the proximal portion of the yeast invertase signal peptide do not block secretion. 639 90

A recombinant cosmid carrying the sucrase gene (sacA) was obtained from a colony bank of E. coli harboring recombinant cosmids representative of the B. subtilis genome. It was shown that the sacA gene is located in a 2kb EcoRI fragment and that the cloned sequence is homologous to the corresponding chromosomal DNA fragment. A fragment of 2kb containing the gene was subcloned in both orientations in the bifunctional vector pHV33 and expression was further looked for in B. subtilis and E. coli. Complementation of a sacA mutation was observed in Rec+ and REc- strains of B. subtilis. Expression of sucrase was also demonstrated in E. coli, which is normally devoid of this activity, by SDS-polyacrylamide gel electrophoresis, specific immunoprecipitation and assay of the enzyme in crude extracts. The specific activity of the enzyme depended on the orientation of the inserted fragment. The saccharolytic activity was found to be cryptic in E. coli since the presence of the recombinant plasmids did not allow the transport of [U14C] sucrose and the growth of the cells. It was shown also that the recombinant cosmid contained part of the neighboring locus (sacP) which corresponds to a component of the PEP-dependent phosphotransferase system of sucrose transport of B. subtilis.
Mol Gen Genet 1982
PMID:Cloning and expression in Escherichia coli of the sucrase gene from Bacillus subtilis. 681 36

Mutants with reduced hexokinase activity previously isolated as resistant to carbon catabolite repression of invertase and maltase (Zimmermann and Scheel, 1977) were allele tested with mutant strains of Lobo and Maitra (1977) which had defects in one or several of the genes coding for glucokinase and the two unspecific hexokinases. It could be demonstrated, that the mutation abolishing carbon catabolite repression had occurred in a gene allelic to the structural gene of hexokinase PII. Moreover, the defective mutant allele for hexokinase PII isolated by Lobo and Maitra (1977) was also defective in carbon catabolite repression. Neither glucokinase nor hexokinase PI showed any effect on this regulatory system. Biochemical analysis in crude extracts also showed altered kinetic properties of hexokinases in the hex1 mutants. The results directly support the hypothesis previously put forward, that one of the hexokinases is not only active as a catalytic, but also as a regulatory protein.
Mol Gen Genet 1980
PMID:Genetic and biochemical evidence for hexokinase PII as a key enzyme involved in carbon catabolite repression in yeast. 699 59

The previously isolated recessive mutant allele hex2-3 of Saccharomyces cerevisiae caused a defect in carbon catabolite repression of maltase, invertase, malate dehydrogenase, and respiration but at the same time led to an extreme sensitivity to maltose (Zimmerman and Scheel, 1977; Entian and Zimmermann, 1980). Addition of maltose to a growing culture of a hex2-3 mutant resulted within 60 to 90 min in an inhibition of growth, glycolysis, and de novo protein synthesis. This was not accompanied by any abnormal levels of glycolysis metabolites or glycolytic enzyme activities. However, inhibitory effects coincided with a dramatic increase in intracellular glucose up to 150 mM relative to cell water as opposed to 2.5 mM in wild-type cells. This abnormal behavior is interpreted as a result of an uncontrolled maltose uptake in hex2 mutants, which in combination with increasing maltase activity results in an accumulation of intracellular glucose. Obviously the amount of available glucose surpassed glycolytic capacity in hex2 mutants. Properties of mutant alleles hex2 and hex1 (see Entian and Zimmermann, 1980) clearly show, that specific gene functions are involved in adapting the rate of sugar uptake into the cell to the actual glycolytic capacity.
Mol Gen Genet 1980
PMID:A defect in carbon catabolite repression associated with uncontrollable and excessive maltose uptake. 700 23

A mutation causing resistance to carbon catabolite repression in gene HEX2, mutant allele hex2-3, causes an extreme sensitivity to maltose when in combination with the genes necessary for maltose metabolism. This provided a convenient system for the selective isolation of mutations in genes specifically required for maltose metabolism and other genes involved in general carbon catabolite repression. In addition to reversion of the hex2-3 allele, mutations in three other genes were detected. These genes were called CAT1, CAT3, and MUR1 and in a mutated form abolished maltose inhibition caused by mutant allele hex2-3. Mutant alleles cat1 and cat3 also restored normal repression in the presence of the hex2-3 allele. Segregants having only mutant alleles cat1 or cat3 were obtained by tetrad analysis. These segregants could not grow on nonfermentable carbon sources. Mutant alleles of gene CAT1 were allelic to a mutant allele cat1-1 previously isolated (Zimmermann et al., Mol. Gen. Genet. 151:95-103). Such mutants prevented derepression not only of the maltose catabolizing system, the selected property, but also of glyoxylate shunt and gluconeogenic enzymes. However, respiratory activities and invertase formation were not affected under derepressing conditions. cat3 mutants had the same phenotypic properties as cat1 mutants. This showed that carbon metabolism in yeast cells is under a very complex and ramified control of repressing and derepressing genes, which are interdependent.
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PMID:New genes involved in carbon catabolite repression and derepression in the yeast Saccharomyces cerevisiae. 705 76

beta-Fructofuranosidase activity was found to be cell-bound in Streptococcus mitis ATCC 903. The following evidence suggests that induction functions as a regulatory mechanism for beta-fructofuranosidase in S. mitis: (1) on transfer of glucose-grown exponential phase bacteria to sucrose medium, the specific activity of beta-fructofuranosidase increased fourfold in the course of one generation; (2) other sugars had no stimulatory effect on the rate of synthesis of beta-fructofuranosidase; (3) the effect of sucrose on the rate of synthesis of beta-fructofuranosidase could be measured within a few minutes. Glucose, fructose and mannose repressed beta-fructofuranosidase. The addition of glucose to bacteria growing on sucrose repressed beta-fructofuranosidase for about one generation. The intracellular concentration of glucose was considerably increased during repression, while the intracellular concentration of glycolytic intermediates did not vary significantly.
J Gen Microbiol 1980 May
PMID:Regulation of synthesis of beta-fructofuranosidase (invertase) in Streptococcus mitis. 742 58

A yeast strain deficient in secreted invertase but expressing a cytoplasmic sucrose synthase has been used to select for potato genes that enable growth on sucrose as the sole carbon source by suppressing the sucrose uptake deficiency. Besides the already known sucrose transporter gene (StSUT1), ten different suppressor clones were identified and characterized. One of these cDNAs (PCP1) enabled efficient growth of the mutant yeast strain and mediated uptake of radiolabeled sucrose. The cDNA encodes a protein of 509 amino acids which is highly hydrophilic and thus does not seem to represent a transporter. Sequence comparisons show that the protein contains zinc finger motifs and shares weak homologies with the Drosophila couch potato gene, which serves as a transcriptional regulator, indicating that PCP1 activates a silent endogenous sucrose uptake system. The other suppressor clones encode either putative transcriptional regulators, protein kinases or enzymes involved in thiamine biosynthesis, ferredoxin reduction or glutamyl tRNA reduction and suppress the phenotype by unknown mechanisms.
Mol Gen Genet 1995 Jun 25
PMID:A novel zinc finger protein encoded by a couch potato homologue from Solanum tuberosum enables a sucrose transport-deficient yeast strain to grow on sucrose. 761 68


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