Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.20 (alpha-glucosidase)
 4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Highly sensitive technique are described for the assay of plasma membrane (5'-nucleotidase, alkaline phosphatase), microsomal (neutral alpha-glucosidase, leucyl-2-naphthylamidase) and biliary canalicular (gamma-glutamyltransferase) enzymes and for nine acid hydrolases (acid phosphatase, phosphodiesterase, beta-glucosidase, alpha-glucosidase, alpha-galactosidase, beta-galactosidase, alpha-mannosidase, N-acetyl-beta-glucosaminidase, beta-glucuronidase) in human liver. 2. Optimum and specific assay systems have been developed which give linear kinetics for all enzymes. 3. The range of enzyme activities in samples of human liver, obtained by closed needle biopsy, and sera have been determined.
Clin Sci Mol Med 1977 Mar
PMID:Enzyme activities in human liver biopsies: assay methods and activities of some lysosomal and membrane-bound enzymes in control tissue and serum. 1 4

1. Enterocytes, isolated from the proximal jejinum and distal ileum of the rat, were homogenized and their organelles separated by isopycnic centrifugation on continuous sucrose density gradients. The distributions of marker enzymes for the principal organelles, RNA and protein were determined in the sucrose gradients and related to the activities per entercocyte. 2. In the jejunum the modal equilibrium densities of the various organelles were: brush borders (1.20), lysosomes (1.20), peroxisomes (1.19), mitochondria (1.17) and basal-lateral membranes (1.13). The values were not significantly different in the ileum. The activities of brush-border enzymes, soluble and mitochondrial malate dehydrogenase, soluble and membrane-associated lactate dehydrogenase and particulate protein content, however, were greater in the jejunal than the ileal enterocytes. 3. Detergent exposed latent alkaline phosphatase activity in jejunal enterocytes and indicated that this enzyme is present not only in the brush border but also in the basal-lateral membrane and soluble fractions of the cell. 4. Isolated jejunal brush-border preprations showed latent activities of both alkaline phosphatase and gamma-glutamyltransferase whereas the activities of alpha-glucosidase and leucyl-beta-naphylamidase were not affected by detergent. Mechanical disruption of these preparations suggested the presence of two forms of alkaline phosphatase in the brush border and provides a technique to assess membrane fragility.
Clin Sci Mol Med 1978 Aug
PMID:Analytical subcellular fractionation studies on enterocytes from the jejunum and ileum of the rat and some properties of brush-border alkaline phosphatase. 2 95

A new series of maltase negative mutants have been isolated from yeast strains carrying the MAL4 gene. These mutants are allelic to the MAL4 gene and fail to ferment maltose, sucrose, and alpha-methylglucoside. Most revertants isolated from these mutants restore the ability to ferment above sugars, and also produce the same levels of maltase as the parental strains. One of the revertants (NA-520-R1), however, ferments maltose slowly, and produces 24 fold less enzyme than the parental strain. Genetic studies revealed that revertant (NA-520-R1), is not a true back mutation but is carrying an extra-genic suppressor, which suppresses the mal4 allele in mutant (NA-520). Since several lines of published evidence indicate that the MAL4 gene is a regulatory gene, it is suggested that the MAL4 gene codes for a regulatory protein, which acts as a positive regulatory element in maltase synthesis.
Mol Gen Genet 1979
PMID:Genetic control of maltase synthesis in yeast. IV. Function of the MAL4 gene: extragenic suppression of a maltase negative mutant. 4 11

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

Glucose represses mitochondrial biogenesis and the fermentation of maltose, galactose and sucrose in yeast. We have analyzed the effect of D-glucosamine on these functions in order to determine if it can produce a similar repression. It was found that glucosamine represses the respiration rate (QO2) but more rapidly than glucose and to a final level slightly higher than in glucose-treated cells. Derepression of the respiration rate following either glucose or glucosamine repression was similar. A two hour lag was followed by a linear increase in QO2 to the derepressed level. Both glucose and glucosamine repressed the level of cytochrome oxidase to the same level. Glucosamine was also found to repress maltose and galactose fermentation but not sucrose fermentation. The derepression of maltase synthesis was inhibited by glucosamine. The constitutive synthesis of maltase was repressed by the addition of glucosamine. Glucosamine was judged to produce a repressed state similar to glucose repression in many respects.
Mol Gen Genet 1977 Oct 24
PMID:An evaluation of D-glucosamine as a gratuitous catabolite repressor of Saccharomyces carlsbergensis. 20 60

Mutants altered in carbon catabolite regulation have been isolated by selecting for mutants of the areA217 strain capable of using acetamide as the sole nitrogen source in the presence of sucrose. In addition to creA mutants described previously be Arst and Cove, strains with mutations in two new genes, creB and cre C, have been found. The creB and creC mutants grow poorly on some sole carbon sources and have low levels of some enzymes of carbon catabolism e.g. beta-galactosidase and D-quinate dehydrogenase. The creB and creC mutants are hypersensitive to fluoroacetate, fluoroacetamide and allyl alcohol in the presence of glucose or sucrose but not glycerol; and the enzymes, acetamidase and alcohol dehydrogenase, are less sensitive to carbon catabolite repression than the wild-type strain. Extracellular protease and alpha-glucosidase enzyme activities are elevated in creB and creC mutants, while L-proline and L-glutamate uptake capacities are lower in both the presence and absence of glucose. Interactions between creA, B and C mutations have been investigated in double mutants, and the dominance properties of creB and creC mutants determined. The results indicate that the creB and creC genes may have a regulatory role in the control of carbon catabolism.
Mol Gen Genet 1977 Jan 18
PMID:Pleiotropic mutants of Aspergillus nidulans altered in carbon metabolism. 32 Apr 55

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

Three maltases have been detected in each of a variety of strains of Saccharomyces. These are present in constant relative amounts in a particular strain and are characterized by reproducible first order thermal decay constants. Four of six mutants, temperature-sensitive for maltose fermentation, lack the maltase of intermediate stability. This deficiency appears to be the basis of the temperature sensitivity, and it is concluded that these strains carry a mutation in the structural gene for that maltase.
Mol Gen Genet 1976 Oct 18
PMID:Thermal inactivation of maltase and its application to temperature-sensitive mutants of yeast. 97 59


1 2 3 4 5 6 7 8 9 10 Next >>