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

---

Query: EC:3.2.1.20 (alpha-glucosidase)
4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genetic and biochemical analyses showed that hexokinase PII is mainly responsible for glucose repression in Saccharomyces cerevisiae, indicating a regulatory domain mediating glucose repression. Hexokinase PI/PII hybrids were constructed to identify the supposed regulatory domain and the repression behavior was observed in the respective transformants. The hybrid constructs allowed the identification of a domain (amino acid residues 102-246) associated with the fructose/glucose phosphorylation ratio. This ratio is characteristic of each isoenzyme, therefore this domain probably corresponds to the catalytic domain of hexokinases PI and PII. Glucose repression was associated with the C-terminal part of hexokinase PII, but only these constructs had high catalytic activity whereas opposite constructs were less active. Reduction of hexokinase PII activity by promoter deletion was inversely followed by a decrease in the glucose repression of invertase and maltase. These results did not support the hypothesis that a specific regulatory domain of hexokinase PII exists which is independent of the hexokinase PII catalytic domain. Gene disruptions of hexokinases further decreased repression when hexokinase PI was removed in addition to hexokinase PII. This proved that hexokinase PI also has some function in glucose repression. Stable hexokinase PI overproducers were nearly as effective for glucose repression as hexokinase PII. This showed that hexokinase PI is also capable of mediating glucose repression. All these results demonstrated that catalytically active hexokinases are indispensable for glucose repression. To rule out any further glycolytic reactions necessary for glucose repression, phosphoglucoisomerase activity was gradually reduced. Cells with residual phosphoglucoisomerase activities of less than 10% showed reduced growth on glucose. Even 1% residual activity was sufficient for normal glucose repression, which proved that additional glycolytic reactions are not necessary for glucose repression. To verify the role of hexokinases in glucose repression, the third glucose-phosphorylating enzyme, glucokinase, was stably overexpressed in a hexokinase PI/PII double-null mutant. No strong effect on glucose repression was observed, even in strains with 2.6 U/mg glucose-phosphorylating activity, which is threefold increased compared to wild-type cells. This result indicated that glucose repression is only associated with the activity of hexokinases PI and PII and not with that of glucokinase.
...
PMID:Glucose repression in Saccharomyces cerevisiae is directly associated with hexose phosphorylation by hexokinases PI and PII. 186 42

Sixteen patients suffering from symptoms suggestive of idiopathic reactive hypoglycaemia and reproducible during an oral glucose tolerance test when plasma glucose was less than or equal to 2.8 mM, were included in an acute, double-blind and cross-over study to test the efficacy of Miglitol (Bay m1099), a new alpha-glucosidase inhibitor versus placebo. Patients were randomized to ingest 100 mg Miglitol or placebo together with a sucrose solution (45 g/m2 body surface), one week apart. During four hours, plasma glucose levels were continuously monitored and plasma insulin and gastric inhibitory polypeptide (GIP) levels were measured at 30-minute intervals; serum C-peptide concentration was determined at 0, 30, 60 minutes and then every hour. The post-load rise in plasma glucose was significantly blunted by Miglitol, as shown by the reduced plasma glucose peak, the diminished early (0-120 min) area under the glycaemic curve and the decreased rate of plasma glucose rise. Thereafter, plasma glucose nadir was significantly raised and rate of plasma glucose fall was slowed by Miglitol with a concomitant improvement in the hypoglycaemic index. Insulin secretion was dampened as indicated by parallel reduction of plasma insulin and serum C-peptide peaks; morever, early area under the insulin curve and total (0-240 min) area under the C-peptide curve were significantly reduced. Decrease of plasma GIP peak and total area under the GIP curve were also significant. During sucrose tolerance test with Miglitol, hypoglycaemic symptoms were significantly alleviated but intestinal side-effects were common. Blunting the insulin response to glucose directly by delaying glucose absorption and indirectly through reducing GIP secretion, may be a valuable therapeutic approach in reactive hypoglycemia; nevertheless, long-term study with Miglitol are needed, due to the poor intestinal tolerance of this drug in the present acute study.
...
PMID:Effect of Miglitol (Bay m1099), a new alpha-glucosidase inhibitor, on glucose, insulin, C-peptide and GIP responses to an oral sucrose load in patients with post-prandial hypoglycaemic symptoms. 188 80

A new substrate, 3-ketobutylidene beta-2-chloro-4-nitrophenylmaltopentaoside (3KB-CNPG5), was used for the determination of alpha-amylase (EC 3.2.1.1) in serum and urine. Under this alpha-amylase assay condition, 3KB-CNPG5 is resistant to glucoamylase and alpha-glucosidase, which are auxiliary enzymes, because the 4- and 6-positions of the non-reducing-end glucose residue are modified by the 3-ketobutylidene group. The assay using 3KB-CNPG5 for alpha-amylase activity is a highly sensitive method that uses 2-chloro-4-nitrophenol (CNP) as an aglycone, and is a stable method for determination of alpha-amylase activity in biological fluids.
...
PMID:Determination of alpha-amylase using a new blocked substrate (3-ketobutylidene beta-2-chloro-4-nitrophenyl-maltopentaoside). 193 99

Total parenteral nutrition (TPN) decreases disaccharidase activity in the small intestine of humans and miniature piglets. The possibility, however, that specific components of TPN (eg, the energy mix) will increase disaccharidase activity has largely been unexplored. The identification of such components would be particularly useful in the treatment of premature infants with immature gastrointestinal tracts and patients with small intestinal mucosal disease associated with decreased disaccharidase activity. To determine whether the TPN energy composition affects small intestinal disaccharidase activity, 7-day-old miniature piglet littermates were randomized to receive TPN containing either glucose (group G) or glucose and fat (group G/F) as the nonnitrogen energy source(s). The TPN regimens were isonitrogenous and isoenergetic. The piglets were not allowed oral intake during the 7 days they were maintained on TPN. At 14 days of age the piglets were killed and the small intestines analyzed for weight, protein, DNA, and disaccharidase activity. Body weight was similar between groups at both the beginning and end of the study. The TPN regimen did not affect small intestinal weight of protein and DNA content. However, jejunal and ileal sucrase and ileal maltase activities (mumol/min.kg body wt +/- SD) were greater in group G than those in group G/F (28 +/- 9 vs 19 +/- 11, p = 0.04; 13 +/- 7 vs 7 +/- 4, p = 0.037; and 31 +/- 8 vs 19 +/- 10, p = 0.0088, respectively). No differences in lactase activity were noted between groups.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Total parenteral nutrition energy composition affects small intestinal disaccharidase activity in the newborn miniature pig. 194 71

Saccharomyces cerevisiae regulatory genes CAT1 and CAT3 constitute a positive control circuit necessary for derepression of gluconeogenic and disaccharide-utilizing enzymes. Mutations within these genes are epistatic to hxk2 and hex2, which cause defects in glucose repression. cat1 and cat3 mutants are unable to grow in the presence of nonfermentable carbon sources or maltose. Stable gene disruptions were constructed inside these genes, and the resulting growth deficiencies were used for selecting epistatic mutations. The revertants obtained were tested for glucose repression, and those showing altered regulatory properties were further investigated. Most revertants belonged to a single complementation group called cat4. This recessive mutation caused a defect in glucose repression of invertase, maltase, and iso-1-cytochrome c. Additionally, hexokinase activity was increased. Gluconeogenic enzymes are still normally repressible in cat4 mutants. The occurrence of recombination of cat1::HIS3 and cat3::LEU2 with some cat4 alleles allowed significant growth in the presence of ethanol, which could be attributed to a partial derepression of gluconeogenic enzymes. The cat4 complementation group was tested for allelism with hxk2, hex2, cat80, cid1, cyc8, and tup1 mutations, which were previously described as affecting glucose repression. Allelism tests and tetrad analysis clearly proved that the cat4 complementation group is a new class of mutant alleles affecting carbon source-dependent gene expression.
...
PMID:Extragenic suppressors of yeast glucose derepression mutants leading to constitutive synthesis of several glucose-repressible enzymes. 200 6

The definite structure and chemical stability of a new glucoside of L-ascorbic acid (AA) which was enzymatically glucosylated with rat intestinal and rice seed alpha-glucosidases were reported. The stability of this AA derivative in water under aerobic conditions was proved by its remarkable resistance against enhanced oxidative degradation by heat, Cu2+ ion or ascorbate oxidase, and it was found to have no reducing activity toward radicals. These properties were obviously distinguishable from those of AA. This glucoside was effectively hydrolyzed by alpha-glucosidases which possessed the ability to synthesize itself, resulting in the liberation of AA activity. The conjugate was composed of equimoles of AA and glucose. Nuclear magnetic resonance spectra, mass spectra, pH profiles of ultraviolet spectra and pK(a) value of 3.10 supported the coupling of alpha-glucose to the 2-position of AA. From these results, its structure was assigned 2-O-alpha-D-glucopyranosyl-L-ascorbic acid, being distinct from 6-O-alpha-D-glucopyranosyl-L-ascorbic acid formed with Aspergillus niger alpha-glucosidase. These findings indicate that the 2-O-glucoside formed by regioselective transglucosylation withstands oxidative degradation even in aqueous solutions and it can be used as an available active AA source for multicomponent liquid products.
...
PMID:L-ascorbic acid alpha-glucoside formed by regioselective transglucosylation with rat intestinal and rice seed alpha-glucosidases: its improved stability and structure determination. 208 81

Rats trained on a diurnal controlled meal-feeding schedule and injected with a single dose of 3,5,3'-triiodothyronine (T3) failed to accumulate liver glycogen and incorporated less D-[6-3H]glucose into glycogen than normally observed during the feeding period. In the experimental group, the concentration of liver adenosine 3',5'-cyclic monophosphate (cAMP) did not fall during feeding and the pattern of activities of glycogen phosphorylase, glycogen synthase, and phosphorylase kinase remained conductive to glycogenolysis. Liver lysosomal alpha-glucosidase activity normally fell during feeding periods. After T3 treatment the activities of alpha-glucosidase and two lysosomal cathepsins (B1 and D) were elevated. The evidence suggests that T3 may induce both liver phosphorylase kinase and lysosomal alpha-glucosidase. This outcome of T3 excess, in concert with previously described T3-inducible systems, provides a plausible explanation for the failure of glycogen accumulation in this experimental model.
...
PMID:Mechanisms underlying enhanced glycogenolysis in livers of 3,5,3'-triiodothyronine-treated rats. 210 55

Acid maltase deficiency in adults is associated with progressive muscle weakness and may effect respiratory muscles resulting in respiratory failure. The biochemical and clinical manifestations of acid maltase deficiency arise from a marked deficiency of the lysosomal enzyme alpha-glucosidase (acid maltase), which normally degrades glycogen to free glucose. In the past few years, high-protein diets have provided an alternative energy source for these patients and resulted in improved muscle strength. Recently, we treated a ventilator-dependent acid maltase-deficient patient with a general diet supplemented with branched-chain amino acids. Branched-chain amino acids are the principal amino acids involved in muscle protein synthesis and utilization. While on this diet, the patient had improvement of respiratory function and muscle strength and was able to be weaned from the ventilator during the day. In addition to his nutritional status, levels of serum branched-chain amino acids, showed improvement within 2 months after the diet started. This diet shows potential advantages over a high-protein diet without supplemented branched-chain amino acids for the treatment of acid maltase deficiency. These include theoretical sparing of amino acids required for muscle protein synthesis by providing higher concentrations of postprandial branched-chain amino acids in the circulation. Also, the liquid formula would be better tolerated by a ventilator-dependent or debilitated patient rather than a high-protein general diet. Further experience with branched-chain amino acid formulas will be needed to substantiate their efficacy in the treatment of acid maltase deficiency.
...
PMID:Treatment of acid maltase deficiency with a diet high in branched-chain amino acids. 211 30

Nucleic acid synthesis in tissues of rapid growth is preferentially done using dietary purines and pyrimidines via the salvage pathway. In the case of a low protein intake, dietary nucleotides may be semiessential for cell replication of gut, lymphocytes, and bone marrow, and especially in those intestinal diseases in which the mucosa is altered, dietary nucleotides may have a role in intestinal development. The effect of dietary nucleotides on intestinal weight and length, gut mucosal weight, intestinal protein and DNA contents, and lactase, maltase, and intestinal mucosal activities was assessed in a controlled way. Weanling (21-day-old) rats were separated into two groups of 36, each receiving blindly a basal diet containing glucose polymers (C) or a basal diet with lactose as the main carbohydrate (L) for 15 days. Those fed with L developed a syndrome of chronic diarrhea and malnutrition. Ten rats of each group were sacrificed at that time. The rest of the animals of each group were separated into two subgroups. The first was fed with the C diet and the second with the C diet supplemented with 50 mg/100 g of each of the following nucleotides: AMP, GMP, CMP, UMP, and IMP (CN). Thus the subgroups CC, CN, LC, and LN were formed. Rats were sacrificed after 4 weeks and gut separated into three segments corresponding to duodenum, jejunum, and ileum. Analysis of variance was used to compare the effect of diet or segments. DNA and lactase, maltase, and sucrase activities increased in the LN group with respect to LC especially in jejunum and ileum but there were not any differences between CC and CN.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Effect of dietary nucleotides on intestinal repair in rats with experimental chronic diarrhea. 212 43

Gentamicin nephrotoxicity is associated with impairments in proximal tubular function. This study determined whether gentamicin administration to the rat, before a reduction in glomerular filtration rate (GFR), causes early and selective alterations in renal cortical brush-border membrane (BBM) enzyme and transport activity, lipid composition, and fluidity. Three days of gentamicin administration caused significant decreases in the Vmax of alkaline phosphatase, the Vmax of sodium gradient-dependent phosphate transport (Na-Pi cotransport), and the Vmax of pH gradient-dependent sodium transport (Na-H exchange). Gentamicin did not affect BBM-bound maltase or leucine aminopeptidase activities and sodium gradient-dependent glucose or proline transport activities. Gentamicin also caused a significant decrease in BBM sphingomyelin, significant increases in BBM phosphatidylcholine and phosphatidylinositol, a significant decrease in the phospholipid fatty acid saturation index, and a significant increase in BBM fluidity, i.e., decrease in the fluorescence anisotropy of diphenylhexatriene. These BBM functional and compositional effects of gentamicin were independent of endogenous parathyroid hormone activity. We conclude that gentamicin causes early and specific alterations in BBM enzyme and transport activity and also lipid composition, which may play an important role in the progression of renal cell injury.
...
PMID:Early selective effects of gentamicin on renal brush-border membrane Na-Pi cotransport and Na-H exchange. 215 23


<< Previous 1 2 3 4 5 6 7 8 9 10

---