Gene/Protein Disease Symptom Drug Enzyme Compound
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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)

The effect of a single oral dose of endosulfan (5 mg/kg body weight) on the uptake of certain nutrients and brush-border enzymes has been studied in rat intestine. The uptake of glucose and alanine was elevated but that of leucine was decreased in endosulfan-fed rats. There was no change in the uptake of phenylalanine and lysine in insecticide-fed rats. The activities of brush-border sucrase and alkaline phosphatase were considerably increased while the activity of Na+ K+ ATPase was reduced in endosulfan-exposed animals. The leucine aminopeptidase activity was unaffected in pesticide-treated rats. There was a significant decrease in cellular LDH and GOT activities with no change in GPT activity. Neither was there a considerable increase in the cellular glucose-6-phosphatase activity (P less than 0.01) in the pesticide-fed rats. These results suggest that endosulfan toxicity induces certain functional changes in the intestine.
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PMID:Effect of a single oral dose of endosulfan on intestinal uptake of nutrients and on brush-border enzymes in rats. 618 May 24

The effect of a single oral dose of pp'DDT (100 mg/kg body wt.) has been studied on the intestinal uptake of certain nutrients and on brush border enzymes in rats. Intestinal uptake of leucine, and phenylalanine was considerably increased but there was no change in the absorption of glucose and alanine in DDT fed rats, compared to controls. The activities of brush border sucrase, alkaline phosphatase and Na+, K+-ATPase were significantly depressed in pesticide treated animals, but leucine aminopeptidase levels remained unaffected under these conditions. Analysis of the chemical composition of the microvillus membranes revealed a considerable enhancement in total lipids, phospholipids and triglyceride contents of the membranes in DDT exposed rats, but membrane protein, sialic acid and cholesterol fractions did not record any change. 1-14C-acetate incorporation into various lipid classes was studied to explain the observed increase in membrane lipids in DDT exposed animals.
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PMID:Effect of a single oral dose of pp'DDT on the absorption of nutrients in vitro and on brush border enzymes in rat intestine. 627 79

The activity of certain enzymes of the energy producing metabolism of the cytoplasmic and mitochondrial compartment and of disaccharidases was determined in jejunal biopsies of 24 chronic alcoholics (CA) and 10 non-alcoholic control subjects (C). The activity of glucokinase, an enzyme of glycolysis, was markedly (44%, p less than 0.05) increased in the biopsies obtained from CA, while the activity of fructose bisphosphatase, an enzyme of gluconeogenesis, was significantly (p less than 0.05) depressed in CA when compared to C. The activity of other glycolytic enzymes was not affected in CA. The activity of L-alanine amino-transferase was lower in CA (p less than 0.05). A reduction was also seen for mean succinate dehydrogenase activity in CA (-30%), however, this difference was not statistically significant. The mean activity of lactase, maltase and sucrase was comparable in both groups.
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PMID:Activities of cytoplasmic, mitochondrial and brush border enzymes in jejunal mucosa of chronic alcoholics. 628 1

The effect of dietary thiamin deficiency has been studied on intestinal functions and chemical composition of brush border membranes in rats. Intestinal uptake of glucose, glycine, alanine, and leucine was significantly stimulated in thiamin deficiency compared to pair-fed control group. Studies with glucose and glycine revealed that stimulation of the absorption process occurs only in the presence of Na+ but not in its absence. Km measured in the presence of 140 mM Na+ for glucose and glycine uptakes was reduced by 56 and 41%, respectively, but Vmax remained unaltered in vitamin deficiency. There was no change in these parameters in Na+-free medium (Km = 31.3 and 23.3 mM; Vmax = 17.2 to 19.7 and 13.5 to 16.4 mumol/10 min/g wet tissue, respectively) under these conditions. The activities of brush border sucrase, lactase, maltase, alkaline phosphatase, and leucine aminopeptidase were reduced by 42 to 66% in thiamin deficiency, compared to pair-fed controls. Kinetic studies with sucrase and alkaline phosphatase evinced that a decrease in Vmax (61 and 64%, respectively) with no change in Km (33.8 and 4.3 mM, respectively) was responsible for observed impairment in the enzyme activities in thiamin deficiency. Microvillus membrane proteins expressed on dry membrane basis were reduced by 20% in thiamin-deficient intestine. There was no difference in membrane sialic acid, cholesterol, phospholipids, and triglycerides fractions under these conditions. It is suggested that thinning of the microvillus membrane may be implicated in observed aberrations of intestinal functions in thiamin-deprived animals.
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PMID:Effect of dietary thiamin deficiency on intestinal functions in rats. 646 54

The effect of exogenous hypercortisolism and 1,25-dihydroxyvitamin D-3 on small-intestinal calcium and glucose transport in the rat was studied at the level of brush-border membrane vesicles generated from isolated villous cells by a freeze-thaw procedure. At 5 X 10(-5) M extravesicular calcium, initial uptake rates in vesicles prepared from triamcinolone-treated adult rats were decreased by 30% after 5 days. Since calcium ionophore A23187 virtually abolished the difference in calcium uptake, triamcinolone appeared to affect calcium channel density or activity rather than intravesicular binding capacity. Kinetic analysis showed that a decrease in Vmax of a saturable calcium transport system could entirely account for the diminished rate of vesicular calcium uptake. Calcium transport rates could be partially restored by in vivo administration of 1,25-dihydroxyvitamin D-3 at a dosage which did not affect vesicular calcium uptake in control animals. Conversely, sodium-driven glucose accumulation in brush-border vesicles from triamcinolone-treated rats was stimulated by 50-70% after 36 h and appeared insensitive to vitamin D. A specific triamcinolone action on the glucose carrier itself rather than on the driving force of the sodium gradient was indicated by (i) a similar stimulation of glucose transport under equilibrium exchange conditions and (ii) an opposite effect of triamcinolone on sodium-driven alanine transport. The triamcinolone-induced changes in calcium and glucose uptake were not accompanied by a gross alteration of membrane integrity in vitro or by major alterations in vesicular protein composition, intravesicular glucose space and sucrase or alkaline phosphatase activity. The modification of vesicular transport properties is discussed in relation to the vitamin D-antagonized inhibition of intestinal calcium uptake and the stimulation of glucose absorption in response to supraphysiologic amounts of glucocorticoids observed in intact epithelium.
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PMID:Calcium and glucose uptake in rat small intestinal brush-border membrane vesicles. Modulation by exogenous hypercortisolism and 1,25-dihydroxyvitamin D-3. 654 50

The effect of folate deficiency, induced by a folate deficient diet, on the digestive and absorptive functions of the intestinal epithelium in rats has been investigated. The intestinal uptake of D-glucose and L-alanine and the brush border sucrase, lactase and alkaline phosphatase activities were considerably depressed in folate deficient animals compared to the control group. Kinetic studies with brush border sucrase in control and deficient animals revealed that reduced levels of the enzyme in folate deficiency are due to a reduced number of enzyme molecules. There was no change in activity of lactate-dehydrogenase in enterocytes of folate deficient rats.
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PMID:Effect of folate deficiency on the digestive and absorptive functions of intestinal epithelium in rats. 679 38

It is well established that Giardia infection causes malabsorption. However, the precise mechanism of such a malabsorption is not known. To investigate this, transport studies, using the tissue accumulation technique, were carried out in mice infected with G. lamblia obtained from human stools. There was a significant fall in the transport of D-glucose, L-alanine and glycine in the infected animals compared with the controls. Kinetics of the D-glucose and glycine transport system were examined by measuring the tissue uptake in the presence of different concentrations of the substrate. For glucose, the affinity constant (Km) for the transport site was the same (4 . 37mM) in normal and infected animals but the maximal transport rate (V max) was considerably reduced in infected animals (158 . 7 mu moles/hr/g tissue) compared with (357 . 1 microgram moles/hr/g tissue) in controls. Results with glycine were similar; the Km was similar in control and infected animals (5 . 7 mM) whereas the V max was reduced in infected animals (27 . 02 microgram moles/hr/g tissue) compared with controls (45 . 5 micrograms moles/hr/g tissue). Analysis of the intestinal enzymes showed a significant decrease in the levels of brush border sucrase, lactase and alkaline phosphatase in infected animals; the cellular enzymes, LDH, GOT and GPT remained unaffected. The observed aberrations in the transport functions and brush border enzymes suggest that G. lamblia causes malabsorption by damaging the epithelial membrane of the enterocyte.
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PMID:Transport studies and enzyme assays in mice infected with human Giardia lamblia. 717 14

The effect of vitamin C deficiency on the digestive and absorptive functions of the gut has been investigated in guinea pigs. The absorption of D-glucose was significantly elevated, but that of L-leucine, L-alanine and L-lysine considerably depressed in the intestine of scorbutic guinea pigs compared to controls. The intestinal transport of vitamin B12 was also diminished. Activities of sucrase and alkaline phosphatase on the brush border were enhanced, but that of leucine aminopeptidase markedly reduced in scorbutic animals compared to controls. Maltase activity was unaffected in vitamin C deficient animals. Chemical analysis of the brush borders isolated from scorbutic animals revealed a considerable decrease in membrane protein, total lipids, phospholipids, and free cholesterol contents compared to control animals. In vivo 2-(14)C-acetate incorporation into membrane lipids suggested that the observed decrease in lipid components of the scorbutic membranes is due to reduced synthesis. Administration of ascorbic acid to scorbutic animals ameliorated the intestinal aberrations observed in scurvy.
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PMID:Effect of vitamin C deficiency in guinea pigs on intestinal functions and chemical composition of brush border membrane. 730 86

The sre gene (ORF469) of the R4 phage encodes a protein similar to the resolvase-DNA invertase family proteins. Insertional gene disruption of sre prevented a lysogen from entering the lytic cycle, implying that Sre protein is a site-specific recombinase needed for excision of the R4 prophage genome (M. Matsuura, T. Noguchi, T. Aida, M. Asayama, H. Takahashi, and M. Shirai, J. Gen. Appl. Microbiol. 41:53-61, 1995). To determine whether this sre gene is also necessary for the integration reaction, we studied its function by integration plasmid analysis. When deletions, frameshifts, and site-directed mutations that caused an amino acid substitution of Ser-17 for Ala were introduced into the sre structural gene, transformation efficiency of Streptomyces parvulus 2297 with these plasmid DNAs was severely reduced. However, an adenine insertion just before the possible initiation codon of the sre gene did not significantly decrease the efficiency. These data suggest that the Sre protein is a site-specific recombinase responsible for integration of the R4 phage genome.
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PMID:The sre gene (ORF469) encodes a site-specific recombinase responsible for integration of the R4 phage genome. 865 26

In a previous study on yeast invertase (Reddy, A., and Maley, F. (1990) J. Biol. Chem. 265, 10817-10820), we identified Asp-23 through the procedures of affinity labeling and site-directed mutagenesis as a catalytic nucleophile. In the present study we undertook to determine other residues involved in the catalytic process. Earlier studies suggested histidine as a potential proton donor in the hydrolysis of sucrose, but by mutagenizing each of the enzyme's four histidines this amino acid was eliminated from consideration. Another candidate appeared to be cysteine, since iodine at about a 2-fold molar excess inactivated invertase by modifying both of the enzyme's cysteine residues. Dithiothreitol treatment restored the sulfhydryl groups and enzyme activity. Replacement of each of the cysteines with alanines revealed that C108A invertase retained full activity whereas C205A was reduced about 4-fold in its kcat. A comparison of the amino acid sequences of fructosylhydrolases revealed a conserved region coincident with Glu-204/Cys-205. Mutagenizing Glu-204 to Ala resulted in a 3, 000-fold reduction in the kcat of invertase indicating that Glu-204 plays a major role in catalysis. Based on these findings, a mechanism is proposed for the hydrolysis of sucrose which involves Asp-23 as a nucleophile and Glu-204 as an acid/base catalyst.
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PMID:Studies on identifying the catalytic role of Glu-204 in the active site of yeast invertase. 866 46


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