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

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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 aim of the present work was to study whether zinc chloride added to the drinking water of rabbits affected the intestinal absorption of D-galactose and the activity of sucrase in the jejunum. The results showed that zinc decreased D-galactose absorption in the jejunal tissue. The effect appeared to be due mainly to an action on the active transport of the sugar by the mucosal border of the intestinal epithelium, because the zinc seemed not to affect its diffusion across the intestinal epithelium. Zinc was also shown to inhibit the (Na(+)-Ka+)-ATPase activity of the enterocyte, which might explain the inhibition of the Na(+)-dependent transport of D-galactose. Nevertheless, a possible direct action of the zinc ion on the Na(+)-dependent carrier cannot be discounted. Zinc did not alter the activity of sucrase in the jejunum of the rabbit.
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PMID:Action of zinc on enzymatic digestion and intestinal transport of sugar in the rabbit. 797 88

The Neurospora plasma membrane H(+)-ATPase is a polytopic integral membrane protein. To localize transmembrane segments, mutants were constructed that contained the amino and carboxyl termini of the H(+)-ATPase with putative transmembrane segment. A stretch of amino acid residues from yeast invertase that has three consensus N-linked glycosylation sites was placed carboxyl terminal of the putative transmembrane segment. RNA transcripts of these mutants were translated in a Neurospora in vitro system that was supplemented with microsomes from Neurospora. By the criteria of glycosylation of the polypeptide chain, resistance to extraction at pH 11.5, and protection from proteinase K digestion, only one transmembrane segment could be identified within the amino acid residues 272-314 of the primary sequence of the H(+)-ATPase.
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PMID:Topology of the Neurospora plasma membrane H(+)-ATPase. Localization of a transmembrane segment. 810 34

We fused the yeast-derived sequences encoding the invertase, acid phosphatase and alpha-factor pre- and prepro-signal peptides (SP) to the Cyamopsis tetragonoloba (guar plant) alpha-galactosidase(alpha Gal)-encoding gene and expressed these gene fusions in yeast. Whereas the amount of fusion protein produced by each of the constructs did not vary significantly, the secretion efficiency of the fusion protein that carried the SP of the prepro-alpha-factor (MF alpha 1) was consistently found to be about 10% higher than that of the other fusions (99% vs. 90%). Furthermore, when the secretion of alpha Gal was directed by the invertase (SUC2) SP, the intracellular enzyme localized to the endoplasmic reticulum (ER), whereas use of the MF alpha 1 SP caused the intracellular enzyme to be outer-chain-glycosylated and processed by the KEX2 endoproteinase, implying that it had passed the ER. These results suggest that the pro-peptide of MF alpha 1 stimulates the efflux of the heterologous protein from the ER. Null mutants of PMR1 (encoding a Ca(2+)-dependent ATPase) are known to give higher secretion efficiencies for a number of different heterologous proteins. Therefore, we also studied the secretion of alpha Gal in a pmr 1 disruption mutant. Structural analysis of the enzyme secreted by the mutant cells showed that it was completely processed by KEX2 and outer-chain-glycosylated, although the length of the outer-chain carbohydrate moiety was reduced when compared with the enzyme secreted by wild-type cells. These results contradict the hypothesis advanced by Rudolph et al. [Cell 58 (1989) 133-145] that disruption of PMR1 causes the secretory pathway to bypass the Golgi apparatus.
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PMID:Effect of a pmr 1 disruption and different signal sequences on the intracellular processing and secretion of Cyamopsis tetragonoloba alpha-galactosidase by Saccharomyces cerevisiae. 838 51

The factors regulating the developmental changes in intestinal morphology and enzyme activity during the postnatal period are incompletely understood. Increased ornithine decarboxylase (ODC) and polyamine levels occur in association with increased mucosal growth seen just prior to weaning. The present work examines the effects of the polyamine spermidine, administered exogenously during early postnatal development in the rat, on structural and functional differentiation of the intestine. Young rats were fed 6 mumol of spermidine for either 1 day (P1) or 3 days (P3) prior to sacrifice on postnatal day 10. Control littermates were sacrificed at day 10 (C10) or at day 49 (C49) (postweanling [adult] reference). A loss of most of the well-developed characteristic endosomal complex and supranuclear giant lysosome was observed in the absorptive cells of the ileum and proximal colon in the spermidine-treated groups and was accompanied by a decline in N-acetyl-glucosaminidase activity to adult levels. A precocious appearance of sucrase and NaK ATPase activities was observed in the P1 group and these activities attained adult levels in the P3 group. This premature appearance of sucrase and NaK ATPase activities was associated with a decline in lactase levels. The exogenous administration of spermidine also elicited an increase in mucosal ODC activity.
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PMID:Effect of exogenously administered polyamine on the structural maturation and enzyme ontogeny of the postnatal rat intestine. 839 Mar 4

Recently, hypertension research has focused on altered cytosolic free Ca2+, [Ca2+]i, in cells of spontaneously hypertensive rats (SHR). In this work, a mechanism(s) responsible for regulating [Ca2+]i was studied with duodenal epithelial cells isolated from SHR and their control, normotensive Wistar-Kyoto rats (WKY). The equal specific activity of sucrase, an enzyme characteristic of microvilli, in both mucosal scrapings and isolated cells from SHR and WKY suggested that mucosal density of enterocytes was not largely different between the two strains. [Ca2+]i of the isolated cells was estimated with fura-2. Upon incubation in the presence of CaCl2, [Ca2+]i increased to a larger extent in SHR than in WKY cells. Ca2+ efflux based on measurements of [Ca2+]i was decreased in SHR cells. Correspondingly, it was found that 45Ca efflux at 10 sec was lower for SHR cells than for WKY cells. Specific activities of Ca(2+)-stimulated and Ca2+/calmodulin-stimulated ATPases in basolateral plasma membrane preparations were reduced in SHR cells. These results indicated that Ca2+ efflux was decreased by reduction in Ca(2+)-pumping ATPase activity in SHR enterocytes.
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PMID:Decreased calcium pump activity in duodenal epithelial cells from spontaneously hypertensive rats. 839 87

To assess the effects of hypothyroidism (HT) on small-intestinal function, HT was induced in rats (120-150 g) by methimazole in drinking water. After 6 wk of methimazole, intestinal absorption studies were performed in HT and in control (C) rats by in situ luminal perfusion of a 20-cm proximal jejunal loop with a bicarbonate buffer containing sodium, glucose or fructose, glycine or lysine, and phenol red as a nonabsorbable marker for determination of water fluxes. Mucosa from the perfused segment was taken for assay of disaccharidases and ATPases and for light and electron microscopy. Compared with C rats, HT rats had significantly lower jejunal transport rates of water (2.54 +/- 0.36 versus 5.02 +/- 0.7 microL/min/microgram mucosal protein, p < 0.03), sodium (37.1 +/- 10.3 versus 102.7 +/- 18.6 mumol/min/microgram protein, p < 0.05), and glucose (1.49 +/- 0.28 versus 5.17 +/- 0.82 mumol/min/microgram protein, p < 0.02). A reduction in glycine transport was also observed but did not attain statistical significance (p = 0.058). Fructose and lysine transport was unchanged. Mucosal sucrase and lactase activities were similar in both groups, but Na,K-ATPase was significantly lower in HT rats (1.17 +/- 0.3 versus 4.03 +/- 1.5 mumol inorganic phosphate/h/mg protein; p < 0.05), with a diminution of ouabain binding sites by 41.5%. Light microscopy of jejunal mucosa from HT rats did not differ from that from C rats; electron microscopy showed mild mitochondrial swelling in HT enterocytes. A group of HT rats were treated with L-thyroxine during 4 wk; these rats had absorption rates, mucosal enzyme activities, ouabain binding, and mucosal morphology not different from C rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of hypothyroidism on jejunal mucosal function: study by in situ luminal perfusion in rats. 839 45

Translocation and integration activities were assessed in Neurospora microsomes (nRM) after modification either by a sulfhydryl alkylating reagent or by a proteinase. A Neurospora in vitro system was programmed with RNA transcripts that encode the amino-terminal 194 amino-acid residues of the Neurospora plasma membrane H(+)-ATPase (pma194+) or the 262 amino-acid residues of the precursor of yeast invertase (preinv262). The processing of preinv262 was blocked in N-phenylmaleimide- and in trypsin-pretreated nRM. In contrast, the binding of preinv262 to microsomes was unaffected in the chemically alkylated nRM, but was affected in the trypsin-pretreated nRM. In the chemically alkylated vesicles, the integration of the pma194+ was not affected, but was partially blocked in the trypsin-pretreated vesicles. These data imply that trypsin-sensitive components are required for these activities in nRM, and that binding, translocation and integration can be differentiated by their sensitivity to chemical alkylation of sulfhydryl groups in nRM. Evaluated also were the effects of temperature on translocation and integration activities in the nRM. These were maximal at 20 degrees C, whereas the binding of preinv262 was maximal at 0 degree C. Taken together, these data demonstrate that the processing of preinv262 by nRM can be resolved into two steps: binding of the precursor protein to nRM and subsequent translocation into the lumen of the vesicles. Whereas, the integration of the pma194+ into nRM could not be resolved into separable steps. Taken together, these results are interpreted to imply that the initial association of truncated forms of the pma+ and the precursor of invertase to the surface of the nRM are distinct processes.
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PMID:The initial association of a truncated form of the Neurospora plasma membrane H(+)-ATPase and of the precursor of yeast invertase with microsomes are distinct processes. 839 89

Erythromycin, an antibiotic used in the treatment of infectious diseases, produces gastrointestinal side effects such as diarrhea. The mechanisms by which erythromycin produces these effects are not known. However, erythromycin has been shown to increase gastrointestinal motor activity and to inhibit intestinal neutral amino acid absorption. Both effects could contribute to the gastrointestinal side effects observed. Because the intestinal systems of amino acid and sugar transport present similar characteristics, the aim of the present work was to determine whether erythromycin also alters D-galactose absorption and sucrase activity in rabbit jejunum. The results show that erythromycin diminishes intestinal D-galactose absorption. This effect seems to be due to an action mainly located on the Na(+)-dependent sugar transport of the mucosal border of the intestinal epithelium. Erythromycin also inhibits the Na(+)-K+ ATPase activity of the enterocyte, which might explain the inhibition of the D-galactose Na(+)-dependent transport. However, a direct action of the erythromycin molecule on the Na(+)-dependent carrier cannot be excluded. Erythromycin did not alter sucrase activity.
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PMID:Effect of erythromycin on D-galactose absorption and sucrase activity in rabbit jejunum. 840 81

We examined the effects of yeast actin NH2-terminal mutations on actomyosin interactions and the function of actin in vivo through measurements of actin-activated ATPase activity, cosedimentation with rabbit muscle myosin subfragment 1 (S-1), in vitro motility, and invertase secretion assays. As reported earlier (Cook, R. K., Blake, W., and Rubenstein, P. A. (1992) J. Biol. Chem. 267, 9430-9436), elimination of NH2-terminal acidic residues from yeast actin results in an increased actin bundling, decreased actin-activated S-1 ATPase, and complete inhibition of actin filament sliding over myosin. Here we show that the addition of 2 new acidic residues to the NH2 terminus of yeast actin increased the Vmax value and the catalytic efficiency of the actin-activated ATPase activity of S-1. However, the binding of actin to S-1 in the presence of ATP and the velocities of actin sliding over myosin in the in vitro motility assays were not affected by this mutation. Thus, the number of actin NH2-terminal negative charges is important for actin activation of myosin S-1 ATPase activity, while only a minimum number of acidic residues is required for actin sliding over myosin in vitro. The number of actin NH2-terminal negative charges therefore appears to determine the efficiency with which the energy from ATP hydrolysis is converted to filament sliding.
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PMID:Enhanced stimulation of myosin subfragment 1 ATPase activity by addition of negatively charged residues to the yeast actin NH2 terminus. 842 14

Erythromycin has been shown to inhibit the intestinal transport of L-threonine and D-galactose in strips of mucosal jejunum when it was directly added to the incubation medium. Nevertheless, the effect of erythromycin administered therapeutically by intramuscular injection on both the intestinal absorption of nutrients and the intestinal digestive activity, remains unknown. The results obtained show that, firstly, the intestinal absorption of L-threonine is inhibited in animals treated with erythromycin. The kinetic study shows that the effect seems to be mainly due to an alteration of the affinity apparent constant (Kt) of the Na(+)-dependent system of transport located in the mucosal border. However, the Na(+)-dependent L-threonine transport in BBMV was not altered by the treatment with erythromycin. The (Na(+)-K+) ATPase activity in BLMV from treated jejunum was 40% of the activity in control BLMV. Secondly, the treatment with erythromycin did not modify the digestive enzymatic activity of sucrase and aminopeptidase N.
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PMID:Study of the action of intramuscularly administered erythromycin on the L-threonine transport and the digestive enzymatic activity in rabbit jejunum. 876 16


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