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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 recessive mutant cat1-1, wild type CAT1, was isolated in Saccharomyces cerevisiae. It did not grow on glycerol nor ferment maltose even with fully constitutive, glucose resistant maltase synthesis. It prevented derepression of isocitrate lyase, fructose-1,6-diphosphatase and maltase in a constitutive but glucose sensitive maltase mutant. Derepression of malate dehydrogenase was retarded and slowed down. Sucrose fermentation and invertase synthesis was not affected. Respiration was normal. From this mutant, two reverse mutants were isolated. One was recessive, acted as a suppressor of cat1-1 and was called cat2-1, wild type CAT2; the other was dominant and allelic to CAT1 and designated CAT1-2d and cat2-1 caused an earlier derepression of enzymes studied but did not affect the repressed nor the fully derepressed enzyme levels. CAT1-2d and cat2-1 did not show any additive effects. It is proposed that carbon catabolite repression acts in two ways. The direct way represses synthesis of sensitive enzymes, during growth on repressing carbon sources whereas the other way regulates the derepression process. After alleviation of carbon catabolite repression, gene CAT1 becomes active and prevents the activity of CAT2 which functions as a repressor of sensitive enzyme synthesis. The CAT2 gene product has to be eliminated before derepression can actually occur. The time required for this causes a delay in derepression after the depletion of a repressible carbon source. cat1-1 cannot block CAT2 activity and therefore, derepression is blocked. cat2-1 is inactive and derepression can start after carbon catabolite repression has ceased. CAT1-2d permanently active as a repressor of CAT2 and eliminates the delay in derepression.
Mol Gen Genet 1977 Feb 28
PMID:Genetics of carbon catabolite repression in Saccharomycess cerevisiae: genes involved in the derepression process. 19 40

Mutants with defective carbon catabolite repression have been isolated in the yeast Saccharomyces cerevisiae using a selective procedure. This was based on the fact that invertase is a glucose repressible cell wall enzyme which slowly hydrolyses raffinose to yield fructose and that the inhibitory effects of 2-deoxyglucose can be counteracted by fructose. Repressed cells were plated on a raffinose--2-doexyglucose medium and the resistant cells growing up into colonies were tested for glucose non-repressible invertase and maltase. The yield of regulatory mutants was very high. All were equally derepressed for invertase and maltase, no mutants were obtained with only non-repressible invertase synthesis which was the selected function. A total of 61 mutants isolated in different strains were allele tested and could be attributed to three genes. They were all recessive. Mutants in one gene had reduced hexokinase activities, the other class, located in a centromere linked gene, had elevated hexokinase levels and was inhibited by maltose. Mutants in a third gene were isolated on a 2-deoxyglucose galactose medium and had normal hexokinase levels. A partial derepression was observed for malate dehydrogenase in all mutants. Isocitrate lyase, however, was still fully repressible.
Mol Gen Genet 1977 Jul 07
PMID:Mutants of Saccharomyces cerevisiae resistant to carbon catabolite repression. 19 90

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.
Mol Gen Genet 1978 Feb 27
PMID:A yeast mutant with glucose-resistant formation of mitochondrial enzymes. 20 62

The two mutants (abs) and (wal) affecting the cell morphology of yeast lead also to higher in vivo activities of the cell wall enzymes acid phosphatase, invertase and melibiase.
Mol Gen Genet 1979 Jun 07
PMID:Pieiotropic effect of two cell wall mutants on the activity of some cell wall enzymes in the yeast Saccharomyces cerevisiae. 22 35

Invertase formation in the yeast Saccharomyces cerevisiae is subject to repression by hexoses in the growth medium. Mutagen-induced (ethyl methanesulfonate or N-methyl-N-nitro-nitrosoguanidine) invertase hyperproducer mutants have been derived from the SUC3 MAL3 strain EK-6B by selecting for their ability to grow on media containing the sugar raffinose plus 2-deoxy-D-glucose (2DG). Raffinose like sucrose is a betta-fructoside which can be hydrolyzed by yeast invertase (beta-fructoside which can be hydrolyzed by yeast invertase (beta-fructofuranoside fructohydrolase). These mutants, designated dgr, produce higher levels of invertase (pi-glucosidase levels are also elevated but to a lesser extent) under conditions normally repressing invertase biosynthesis in the parent. Invertases of mutants dgr2 and dgr3 are indistinguishable from that of EK-6B with respect to their Km's for sucrose and thermal labilities. Genetic studies revealed that dgr2 and dgr3 are recessive and unlinked to the SUC3 gene.
Mol Gen Genet 1978 Sep 08
PMID:Genetic control of invertase formation in Saccharomyces cerevisiae. II. Isolation and characterization of mutants conferring invertase hyperproduction in strain EK-6B carrying the SUC3 gene. 36 57

1. Specimens of human duodenal mucosa were obtained at duodenotomy. Superficial mucosal scrapings were homogenized in isotonic sucrose solution and fractionated by differential centrifugation. The distribution of organelles among the subcellular fractions was monitored by assay of suitable marker enzymes. 2. Enterokinase was recovered predominantly in the nuclear+brush-border fraction and 80% of the total activity was found to be particulate; approximately 20% of the enzyme was present in the soluble fraction, compared with 1% of the brush-border markers sucrase and alkaline phosphatase. 3. The brush-border-containing fraction was subfractionated by treatment with hypertonic Tris followed by differential and density gradient centrifugation. Enterokinase was distributed among the subfractions in parallel with brush-border markers and was concentrated in a subfraction which was highly enriched in microvillous membranes. 4. It was concluded that enterokinase is localized primarily to the microvillous membrane of the epithelial cell brush border in man, but that in addition a proportion of the enzyme may be present in a soluble or easily released form in the duodenal mucosa.
Clin Sci Mol Med 1977 Dec
PMID:Subcellular localization of enterokinase in human duodenal mucosa. 58 40

1. Rats were fed with the elemental diet Vivonex for 1 or 3 months and their jejunal histology was compared with that of an equal number of rats fed on a normal diet. 2. After 1 month of Vivonex feeding a significant reduction in the ratio of crypt height: villus height (CH:VH) was found in the Vivonex-fed rats (n = 4) compared with the control rats (n = 4) (P less than 0.05). 3. After 3 months the CH:VH ratio was also reduced in the Vivonex-fed rats (n = 18) compared with control rats (n = 18) (P less than 0.002). Villus height was significantly increased (P less than 0.002) and crypt height decreased (P less than 0.05). 4. Jejunal protein content, alkaline phosphatase and disaccharidase activity were also determined in 12 control and 12 Vivonex-fed rats from the 3 months study. 5. Alkaline phosphatase activity was increased from a control value of 201 +/- 8 to 243 +/- 15 munits/cm in the Vivonex-fed rats (n = 12) (P less than 0.05) but no significant changes in lactase, sucrase or maltase activites were found. The observed decrease in the CH:VH ratio suggested an improved survival of the mature enterocyte population during elemental diet feeding.
Clin Sci Mol Med 1978 Nov
PMID:Small-intestinal changes induced by an elemental diet (Vivonex) in normal rats. 72 6

The role of mitochondria in carbon catabolite repression in Saccharomyces cerevisiae was investigated by comparing normal, respiratory competent (RHO) strains with their mitochondrially inherited, respiratory deficient mutant derivatives (rho). Formation of maltase and invertase was used as an indicator system for the effect of carbon catabolite repression on carbon catabolic reactions. Fermentation rates for glucose, maltose and sucrose were the same in RHO and rho strains. Specific activities of maltase and invertase were usually higher in the rho-mutants. A very pronounced difference in invertase levels was observed when cells were grown on maltose; rho-mutants had around 30 times more invertase than their RHO parent strains. The fact that rho-mutants were much less sensitive to carbon catabolite repression of invertase synthesis than their RHO parents was used to search for the mitochondrial factor(s) or function(s) involved in carbon catabolite repression. A possible metabolic influence of mitochondria on this system of regulation was tested after growth of RHO strains under anaerobic conditions (no respiration nor oxidative phosphorylation), in the presence of KCN (respiration inhibited), dinitrophenol (uncoupling of oxidative phosphorylation) and of both inhibitors anaerobic conditions and dinitrophenol had no effect on the extent of invertase repression. KCN reduced the degree of repression but not to the level found in rho-mutants. A combination of both inhibitors gave the same results as with KCN alone. Erythromycin and chloramphenicol were used as specific inhibitors of mitochondrial protein synthesis. Erythromycin prevented the formation of mitochondrial respiratory systems but did not induce rho-mutants under the conditions used. However, repression of invertase was as strong as in the absence of the inhibitor. Chloramphenicol led only to a slight reduction of the respiratory systems and did not affect invertase levels. A combination of both antibiotics had about the same effect as growth in the presence of KCN. The results showed that mitochondria are involved in carbon catabolite repression and they cause an increase in the degree of repression. These effects cannot be due to mere metabolic activities nor to factors made on the mitochondrial protein synthesizing machinery. This regulatory role of mitochondria is observed as long as an intact mitochondrial genome is maintained.
Mol Gen Genet 1976 Oct 18
PMID:The role of mitochondria in carbon catabolite repression in yeast. 79 Jan 58

In this study the influence of 14 antibiotics, 12 of them orally applicable, on human enterokinase was investigated. The effects of these substances on the activities of human disaccharidases were also examined. The enterokinase activity is more sensitive to the studied antibiotics than is human lactase, saccharase or isomaltase. Unphysiologically high concentrations of penicillins, cephalexin and chloramphenicol (10(-2) Mol/l) inhibited enterokinase, tetracycline (doxycycline) in a dose of 10(-3) m reduced the activity of this enzyme by 50%, neomycinsulphate and the sulphates of polymyxin B and E have no effect on the disaccharidases. On the contrary, these substances are the best inhibitors of enterokinase among the tested antibiotics. Neomycin or polymyxin (10(-4) Mol/l) causes a 50% inhibition of a physiological quantity of this enzyme. Therapeutic doses of both antibiotics may reduce the enterokinase activity by 70% to 90%, while the activity of trypsin is not affected unless a concentration greater than 10(-2) m is used. The inhibition is not only caused by the anion (SO4) of these antibiotics, since sulphates reduce the enterokinase only in concentrations higher than 10(-3) Mol/l in man. The mechanism of inhibition is not effected by binding cholic acids under test conditions. Both polymyxin and neomycin inhibit the enterokinase activity with and without glycodeoxycholic acid. Further studies showed that the type of inhibition is competitive in both cases. The inhibition constant K2 of neomycin-B-sulphate is 8.7X10(-5) Mol/l, of polymyxin-E-sulphate 8.6X10(-5) Mol/l. The inhibition type of penicillins, cephalosporins and doxycycline is noncompetitive, thus contrasting that of neomycin and polymyxin.
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PMID:[The influence of orally applicable antibiotics on the activities of human enterokinase and disaccharidases (author's transl)]. 98 20

The RNA polymerase inhibitor, lomofungin has been used to determine the half life of specific synthetic capacities (invertase and alpha-glucosidase) as well as that for gross protein synthesis. In both cases the studies conclude that cognate messenger RNAs decay with a half life of approximately 20 minutes. This antibiotic has been used to determine the half life of allophanate hydrolase specific synthetic capacity. We find that it decays with a half life of about three minutes; a value that agrees with the decay rates of allophanate hydrolase synthetic capacity following removal of inducer. These observations argue that mRNA may be metabolized by two separate routes in Saccharomyces.
Mol Gen Genet 1975
PMID:Lomofungin inhibition of allophanate hydrolase synthesis in Saccharomyces cerevisiae. 110 15


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