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

Effects of the dopamine agonist 2-bromo-alpha-ergocryptine (bromocriptine) on plasma and pituitary PRL and enzyme activities in lactating and postlactating rats have been investigated. Lactating rats which had been suckling their young for 3 days were given a single sc injection of bromocriptine or solvent. The treated and control animals were divided into 2 further groups. One group (lactating rats) was permitted to suckle their pups for a further 12 or 24 h; the young were removed from the other group (postlactating rats). Homogenates were prepared from the anterior pituitaries and assayed for organelle marker enzyme activities. When 0.5-500 micrograms bromocriptine were administered to lactating rats for 24 h, pituitary PRL was increased by all doses, but only the 500-micrograms dose significantly reduced plasma PRL. Total protein was unchanged, lysosomal acid PRL proteolytic activity increased 8-fold, N-acetyl-beta-glucosaminidase and beta-glucuronidase (lysosomes) were unchanged, acid phosphatase (lysosomes and endoplasmic reticulum) was increased by three of four doses, 5'-nucleotidase and alkaline phosphatase (plasma membrane) were increased 4-fold, neutral-alpha-glucosidase (endoplasmic reticulum) and malate dehydrogenase (mitochondria) were unchanged, and catalase (peroxisomes) was significantly increased. Bromocriptine (500 micrograms) administration to lactating and postlactating rats for 12 and 24 h significantly decreased the pituitary DNA but not the total protein content of the pituitaries in all animals. The lysosomal acid PRL proteolytic activity and the lysosomal enzyme activities, N-acetyl-beta-glucosaminidase and beta-glucuronidase, were increased by suckling withdrawal alone. Acid PRL proteolytic activity was further increased (to 18-fold) by coadministration of bromocriptine, whereas the increase in the activities of the other lysosomal marker enzymes was blocked. Malate dehydrogenase activity (mitochondria) was also increased by litter removal and blocked by bromocriptine. The activity of the plasma membrane markers 5'-nucleotidase and alkaline phosphatase were increased by litter removal, and bromocriptine further increased both enzyme activities. The activity of neutral-alpha-glucosidase (endoplasmic reticulum) was unchanged by any treatment. The results demonstrate that bromocriptine produces significant changes in the activities of lysosomal marker enzymes, particularly acid PRL proteolytic activity, as well as marker enzymes of plasma membranes and other organelles in pituitaries of lactating and postlactating rats.
Endocrinology 1984 Sep
PMID:Effects of bromocriptine on pituitary organelle marker enzyme activities in lactating and postlactating rats: selective activation of lysosomal prolactin proteolytic activity. 608 93

One of the cyr 1 mutants (cyr 1-2) in yeast produced low levels of adenylate cyclase and cyclic AMP at 25 degrees and was unable to derepress acid phosphatase. Addition of cyclic AMP to the cyr1-2 cultures elevated the level of repressible acid phosphatase activity. The bcy1 mutation, which suppresses the cyr1-2 mutation by allowing activity of a cyclic AMP-independent protein kinase, also allows acid phosphatase synthesis without restoring adenylate cyclase activity. The CYR3 mutant had structurally altered cyclic AMP-dependent protein kinase and was unable to derepress acid phosphatase. The cyr1 locus was different from pho2, pho4 and pho81, which were known to regulate acid phosphatase synthesis. Mutants carrying cyr1-2 and pho80, PHO81c, PHO82 or pho85 mutations, which confer constitutive synthesis of repressible acid phosphatase, produced acid phosphatase. The cyr1-2 mutant produced significantly low levels of invertase and alpha-D-glucosidase. These results indicated that cyclic AMP-dependent protein kinase exerts its function in the synthesis of repressible acid phosphatase and other enzymes.
Genetics 1984 Sep
PMID:Regulation of repressible acid phosphatase by cyclic AMP in Saccharomyces cerevisiae. 609 Feb 71

Three therapeutic inhibitors of vertebrate alpha-glucosidases recently assayed in research on diabetes control, show high inhibitory potencies towards the p-NP-alpha-D-glucosidase activity of honeybee haemolymph. BAYe 4609 is an allosteric V-type (pure non-competitive) inhibitor with: Ki congruent to K'i congruent to I50 congruent to 180 micro M; n = 1.17; ni = 1.15 BAYg 5421, an hydrolysis derivative of the former, is a mixed allosteric inhibitor with: Ki congruent to 0.17 micro M; K'i congruent to 0.85 micro M; I50 congruent to 0.38 micro M; n = 1.19; ni = 1.25. BAYn 5595 isd a pure competitive Michaelian inhibitor with: Ki = 15 micro M; I50 congruent to 23 micro M. All these properties reveal similarities to and differences from those of the natural inhibitors of the enzyme and analogies with their action on vertebrate enzymes. Accordingly, correlations have been emphasized between the structure and the activity of these inhibitors which finally lead to propositions of structures for new active molecules.
Biochem Pharmacol 1982 Sep 01
PMID:Kinetic study of the inhibition of the honeybee haemolymph apha-glucosidase in vitro by BAYe 4609, BAYg 5421 and BAYn 5595. 621 20

The digestion of Neosugar, a mixture of 1F-(1-beta-fructofuranosyl)n-1 sucrose [n = 2, 1-kestose (GF2); n = 3, nystose (GF3); n = 4, 1F-beta-fructofuranosyl nystose (GF4)] was investigated in vitro and in vivo by using the rat. The results obtained were as follows. GF2 and GF3 were not hydrolyzed by a pancreatic homogenate. The GF2- and GF3-hydrolyzing activities of the enzymes in the intestinal mucosa homogenate were negligible compared with the activities of maltase and sucrase. GF2 and GF3 added to the incubation mixture did not affect the activities of sucrase and maltase in the intestinal mucosa. Long-term ingestion of Neosugar did not cause induction or suppression of GF2- and GF3-hydrolyzing enzymes in the small intestine. [U-14C]Neosugar injected intravenously was rapidly excreted in the urine without having undergone any degradation. These results indicate that Neosugar, which consists of GF2, GF3 and GF4, is scarcely hydrolyzed by the digestive enzymes of the gastrointestinal tract and internal organs, and that suggests to us that Neosugar is not utilized as an energy source in the body.
J Nutr 1984 Sep
PMID:Nondigestibility of a new sweetener, "Neosugar," in the rat. 633 83

The transport of maltose in Saccharomyces cerevisiae has been generally accepted as a H+-sugar symport, with a stoichiometrical ratio of 1:1. A simultaneous exit of K+ from the cells with the initial uptake of maltose has been reported previously. By using a K+-selective electrode and radioactive maltose, we were able to measure the exit of 1 mol of K+/mol of maltose taken up by the cells in the first 10-15 s. This stoichiometrical ratio is pH-independent. So, uptake of protons in a non-buffered cell suspension or exit of K+ in a buffered one can be used to measure initial rates of maltose uptake. We have used a K+ electrode and a pH electrode to study the effect of external pH and K+ respectively on the kinetic parameters of maltose transport. The following results were obtained: the apparent half-saturation constant for maltose (Km) increased from 5.2 mM at pH 5.8 to 38.0 mM at pH 7.8; the same increase in pH halved the apparent maximum uptake rate (Vmax); K+ had an inhibitory effect, decreasing Vmax. and increasing Km at pH values above 5; K+ had a stimulating effect at pH values below or equal to 4. Under physiological conditions, i.e. lower pH outside, neutral pH inside and much higher [K+] inside the cell, and assuming symmetry of the system, a higher affinity for maltose is to be expected in the outer face of the plasma membrane. This behaviour of the system could explain, by itself, the maintenance of the high concentration of free maltose inside the cell (necessary because of the low affinity of the maltase), without significant back transport to the outside.
Biochem J 1984 Sep 01
PMID:Transport of maltose in Saccharomyces cerevisiae. Effect of pH and potassium ions. 638 58

The formation of intestinal villi (organogenesis phase) may be studied in organ culture with a completely synthetic medium in 15-day fetal mouse duodenal explants. However, in these explants absorptive cells remained poorly differentiated with all the hormones studied except with epidermal growth factor. In order to elucidate the role of hormones and other factors on the maturation of absorptive cells (maturation phase) in the fetal rodent in organ culture, we have taken the explants after the organogenesis phase. We have studied different culture conditions and have found that 17-day mouse duodenal explants can be cultured during 48 hours with Leibovitz L-15 medium in a 95% O2-5% CO2 atmosphere provided that the explants are relatively large (5 X 2 mm). With this method, dexamethasone (Dx) has been shown to have a direct effect on the maturation of the fetal duodenal mucosa. The addition of Dx (300 ng/ml) to the completely synthetic medium 1) improves the morphology of the explants, 2) induces a significant increase in maltase activity in the tissues, and 3) reduces significantly the labeling index of the duodenal explants after 48 hours of culture. Direct action of Dx on the duodenal mucosa is shown for the first time in organ culture using a completely synthetic medium. This method will permit us to study the effects of other intrinsic and extrinsic factors on the regulation of enzymatic maturation in fetal small intestine.
Anat Rec 1984 Sep
PMID:Effect of dexamethasone on the fetal mouse small intestine in organ culture. 638 76

The antinutritional effect caused by the ingestion of lectins from two Brazilian varieties of beans: Rico 23 and Jalo, was studied in rats. The two varieties were selected in a previous screening of toxicity in rats: one of them (Jalo) was lethal, and the other (Rico 23) was not, when injected intra-peritoneally. Different amounts of each one of the lectins were added to casein experimental diets and fed to rats. The amount of protein (casein) also varied from 5% to 20%. The addition to the diet of 1% lectins from the Jalo variety caused a growth depression, as well as a decrease in food efficiency ratio and serum glucose; also, it reduced the maltase and invertase activity of the intestinal mucosa. All these effects appeared when the protein contents in the rations were 5% or 10%. At the 20% level only a depression of the maltase activity was observed. Similar effects were shown by the lectins of the Rico 23 variety, but only when added in a higher (5%) percentage to the diet. The phosphatase and protease activity were not changed by any of the lectins. The inhibitor activity that occurred in vivo was not detected in vitro.
Arch Latinoam Nutr 1984 Sep
PMID:[Antinutritional effect of phytohemagglutinins of Phaseolus vulgaris L]. 639 38

Brush border membrane vesicles from rat small intestine were isolated by a Mg/EGTA precipitation method. Further fractionation either by free flow electrophoresis or by sucrose density gradient centrifugation leads to subfractions which differ with respect to enzyme enrichment factors, transport properties for D-glucose and protein pattern analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. A relative enrichment of (Na+ + K+)-ATPase is found in one fraction, whereas in another fraction maltase, aminopeptidase M and alkaline phosphatase are relatively enriched. The fractions show different properties of D-glucose transport under tracer exchange conditions and a different inhibition of D-glucose transport by phlorizin and phloretin. These results indicate that the vesicles obtained from rat small intestine by this cation precipitation method are not homogeneous. The inhomogeneity cannot be due to a crosscontamination by membranes other than from the cell envelopment, as none of the fractions show a significant enrichment of succinate--cytochrome c oxidoreductase, KCN-resistant NADH oxidoreductase or glucosaminidase. The inhomogeneity might be due either to a crosscontamination by basal-lateral membranes or to membranes derived from epithelial cells not yet fully differentiated.
Eur J Biochem 1983 Sep 01
PMID:Heterogeneity of brush-border-membrane vesicles from rat small intestine prepared by a precipitation method using Mg/EGTA. 641 69

Rabbit intestinal glucoamylase-maltase was examined in detail with respect to its molecular weight, sedimentation, diffusion and viscosity. It is a large asymmetrical molecule, with a molecular weight of 750 000-760 000. Its appearance under the electron microscope supports the idea that it is a long string (62.0 nm) consisting of eight beads of diameter 6.0 nm each and a surface-to-surface interbead distance of approx. 2.0 nm. The shape of the enzyme derived from its hydrodynamic behaviour by using the string-of-spherical-beads model originally proposed by Kuhn [(1932) Z. Phys. Chem. Abt. A 161, 1-32] and later modified by Shulman [(1953) J. Am. Chem. Soc. 75, 5846-5852] fits moderately well with the electron-microscopic picture. The beads might represent about six subunits, and the absence of sulphur from the enzyme and the inability to dissociate the enzyme by conventional methods indicate the possibility of unusual covalent cross-linking between the subunits and between the beads.
Biochem J 1983 Sep 01
PMID:Studies on the size and shape of rabbit intestinal glucoamylase-maltase complex. 641 89

Jejunal fluid and mucosal tissue were obtained simultaneously from the same jejunal site in a group of 29 children by a modified biopsy procedure. Lactase, maltase, and sucrase activities were measured in both fluid and mucosal specimens using the same analytical method. The fluid enzyme activities showed highly significant positive correlations with the same enzyme activity in the relevant tissue samples. Relative concentrations of disaccharidase enzymes represented by sucrase: lactase activity ratios also showed a highly significant positive correlation between fluid and tissue. This close relation suggests that the mucosa is the sole or predominant source of disaccharidase activity in the intestinal fluid. The results of kinetic studies comparing tissue and fluid enzyme characteristics also indicate a mucosal origin for the fluid enzyme activities. We conclude that disaccharidase activities in jejunal fluid reflect closely local tissue values and that these measurements may be useful in assessing mucosal enzyme activity in infants in whom jejunal biopsy is not possible.
Arch Dis Child 1983 Sep
PMID:Disaccharidase activities in jejunal fluid. 641 85


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