Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The carbohydrate-recognition domain of rat serum mannose-binding protein A has been subjected to random cassette mutagenesis. Mutant domains, expressed in bacteria, were initially screened for binding to invertase-coated nitrocellulose and then analyzed further for Ca2+ affinity, saccharide binding, resistance to proteolysis, and oligomerization. The results are consistent with previous evolutionary and structural studies. Six out of seven completely inactive mutants have changes in residues directly involved in ligating Ca2+. Most changes in conserved residues which form part of the hydrophobic core characteristic of Ca(2+)-dependent (C-type) animal lectins result in decreased affinity for Ca2+, even though these residues are distant from the Ca2+ sites. Changes can be made in large portions of the surface without affecting saccharide binding. The results indicate that the precise arrangement of the regular portion of the domain containing the hydrophobic core is necessary for formation of a stable Ca(2+)-ligated structure under physiological conditions. The data also suggest that the saccharide-binding site is likely to be in close proximity to the bound Ca2+.
 ...
PMID:Role of conserved and nonconserved residues in the Ca(2+)-dependent carbohydrate-recognition domain of a rat mannose-binding protein. Analysis by random cassette mutagenesis. 158 59

Saccharomyces cerevisiae Man9-alpha-mannosidase, responsible for trimming Man9GlcNAc2 in the endoplasmic reticulum to Man8GlcNAc2, the substrate for oligosaccharide elongation, has been purified to homogeneity from stabilized microsomal membranes without employing autolytic digestion. The activity was solubilized by the zwitterionic detergent, 3-[(3-cholamidopropyl)dimethyl ammonio]-1-propanesulphonate (CHAPS), whose presence was necessary for maximal activity. Purification included Q-Sepharose ion-exchange chromatography, preparative isoelectric focusing and HPLC gel filtration on TSK 3000 matrix. Overall purification from post-nuclear supernatants was estimated to be 110,000-fold with a 50% recovery of activity. The purified enzyme hydrolysed Man9GlcNAc1,2 from thyroglobulin or oligosaccharide-lipid, but not invertase Man9GlcNAc, Man1 alpha 2Man1 alpha OCH3 or p-nitrophenyl-alpha-D-mannopyranoside. Conversion of thyroglobulin Man9GlcNAc to Man8GlcNAc was linear with time and enzyme concentration, with an apparent Km of 0.2 mM and a specific activity of 220 IU/mg. Glc3Man9GlcNAc2 from oligosaccharide-lipid was as good a substrate as Man9GlcNAc, but the lipid-linked Man7GlcNAc2 isomer was hydrolysed at only 10% of this rate. Hydrolysis of defined isomers of IgM and bovine thyroglobulin Man6,7,8GlcNAc indicated that, for maximal alpha 1,2-mannosidase activity, only the alpha 1,2-linked terminal mannoses on the alpha 3 branch of the Man9GlcNAc precursor were dispensable. Isomers lacking the terminal alpha 1,2-linked mannose on the alpha 6 branch were hydrolysed at only approximately 10% of the maximal rate. The enzyme exhibited a pI of 5.3 and a pH optimum at 6.5. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis in the absence of reducing agents gave a single sharp band at 66 kDa, while in the presence of beta-mercaptoethanol equimolar amounts of two peptides, one of 44 kDa and one of 23 kDa, were obtained. Sizing on Sephacryl SF300, Superose 12 and TSK 3000 provided a holoenzyme mol. wt of 60-68 kDa, indicating that the isolated active form of the Man9-alpha-mannosidase was composed of one each of the sulphydryl-bonded dissimilar peptides. The enzyme bound to concanavalin A (ConA)-Sepharose and was eluted with alpha-methylmannoside, indicating the presence of high-mannose oligosaccharides. The Man9-alpha-mannosidase required low levels of Ca2+, which could be removed by EGTA. Activity was restored by Ca2+ or Zn2+, but not by Mg2+ or Mn2+.
 ...
PMID:Glycoprotein biosynthesis in yeast: purification and characterization of the endoplasmic reticulum Man9 processing alpha-mannosidase. 182 40

Calcium-dependent and -independent bovine IgG reactive with invertase were isolated by affinity chromatography on invertase-coupled Sepharose 4B and their specificities were determined by competitive binding assays. The binding of 125I-labeled calcium-dependent and -independent bovine IgG reactive with invertase to invertase-coupled Sepharose 4B were most effectively inhibited by invertase and mannan. The binding was more weakly inhibited by mannose, glucose, and methyl alpha-D-mannopyranoside, whereas that was much more weakly inhibited by other monosaccharides and glycoproteins. These findings suggest that the combining sites of calcium-dependent and -independent bovine IgG reactive with invertase may be specific for invertase and/or mannan.
 ...
PMID:Immunochemical studies on the combining sites of bovine immunoglobulins reactive with invertase. 183 Jul 59

Oral administration of the antiulcerogenic drug, cimetidine, was studied on kidney-bound hydrolytic enzymes at three different dose levels (30 mg, 100 mg, and 2000 mg/kg body weight) and for single administration for 2 and 24 h, and daily administration for 15 days in mice. It significantly inhibited Na+, K(+)-ATPase, Mg(2+)-ATPase, and Ca2+, Mg(2+)-ATPase in the isolated basolateral membrane (BLM). Brush-border-membrane-(BBM)-associated enzymes, sucrase, lactase, maltase, leucine aminopeptidase, and alkaline phosphatase also showed a marked reduction. Substrate saturation kinetics revealed the nature of inhibition was of mixed type in the case of sucrase, lactase, maltase, and alkaline phosphatase (Km was increased, while Vmax decreased), whereas it was of non-competitive type for leucine aminopeptidase (Km was unchanged, while Vmax decreased). In vitro addition of cimetidine (5-20 mM) to the BBM also inhibited the enzyme activity. Dixon plot produced the inhibition constant (Ki) for cimetidine in the case of maltase, alkaline phosphatase, and leucine aminopeptidase in the order of 14.83, 32.83 and 11.5 mM, respectively. Analysis of lipids revealed a significant reduction in BBM-associated phospholipid and phospholipid/cholesterol molar ratio, while the neutral lipid fraction, i.e., cholesterol and triglycerides were not altered. Free fatty acid exhibited an increase after drug treatment, which was significant at higher dose after 24 h of single and 15 days of daily treatment. BLM-associated lipids did not exhibit any significant change. Cimetidine-induced depression in renal BLM- and BBM-associated disaccharidases and ATPases, at least at the higher dose level, may have serious consequences in the absorption of end-product nutrients.
 ...
PMID:Depression of membrane-bound hydrolases by cimetidine in mouse renal basolateral and brush border. 183 34

The effect on rats of oral doses (38.66 mM/kg body wt) of propane-1,2-diol (PD) administered daily for 10 (Group 1), 20 (Group 2), and 30 days (Group 3) was investigated. Weight gain was initially retarded (P less than 0.05) in Group 1, but was later reversed and elevated significantly (P less than 0.05) in Groups 2 and 3 as compared with their respective controls receiving an equal volume of saline. PD showed a tendency toward enhancing the activities of various enzymes involved in terminal digestion, with the significant effect exerted in few groups on sucrase (P less than 0.05), lactase (P less than 0.05), and gamma-glutamyl transpeptidase (P less than 0.05) when compared with the respective controls. Absorption of D-glucose, glycine, L-aspartic acid, L-lysine, and calcium was elevated and was especially significant in Groups 2 and 3 (P less than 0.001). The structural integrity of the jejunal surface was retained for the most part. A similar examination of the effects of PD was also carried out in vitro to ascertain whether PD itself or its metabolites are involved in its action. The in vitro effects of propane-1,2-diol were compared with those of the more toxic compound propane-1,3-diol. The former exerted greater inhibitory action on the activities of the disaccharidases. The degree of inhibition was in the order sucrase much greater than lactase greater than maltase. The kinetic data revealed that inhibition by 1,2-diol in native and detergent solubilized sucrase is noncompetitive, with Ki values in the range of 0.35-0.41 M. The two diols did not alter the nutrient transport in the brush border membrane vesicles. The present work on rats indicates that PD may influence the intestinal digestive and absorptive functions in vivo and that this in vivo effect of PD is different from that observed in vitro suggesting that the nutritional and toxicological effect of PD may be mediated by different mechanisms.
 ...
PMID:The effect of propane-diols on the intestinal uptake of nutrients and brush border membrane enzymes in the rat. 188 24

Oral administration of embelin (75 mg/kg per day, daily for 15 and 30 days) to male rats caused significant elevation in the uptake of D-glucose, L-alanine, L-leucine and calcium in small intestinal segments. Embelin also produced significant increases in intestinal brush border membrane-associated enzymes (sucrase, lactase, maltase, alkaline phosphatase and leucine aminopeptidase) in both intestinal homogenates and partially purified brush border membrane preparations. Significant increases were also noted for microsomal glucose-6-phosphatase and cytosolic lactate dehydrogenase. Increase in brush border membrane-associated total lipids, phospholipids, cholesterol, triacylglycerol, unesterified fatty acids and ganglioside sialic acid were seen but not in the cholesterol/phospholipid molar ratio. All these changes returned to control or near control levels following withdrawal of the drug.
 ...
PMID:Effects of embelin, a male antifertility agent, on absorptive and digestive functions of rat intestine. 192 15

Fifty two strains of anaerobic bacteria isolated from the upper gut of patients with small intestinal bacterial overgrowth were screened for phospholipase activity. Bacteroides melaninogenicus spp intermedius had the greatest activity. The effects of culture supernatants of this organism and deoxycholate on intestinal calcium absorption and disaccharidase activity were studied using a rat closed loop model. The supernatant decreased the in vitro uptake of calcium by 15% (p less than 0.001). Deoxycholate reduced calcium uptake by 16% (p less than 0.001). Combined culture supernatant and deoxycholate reduced calcium uptake by 39% (p less than 0.001) suggesting a potentiation of supernatant activity by deoxycholate. Culture supernatant and deoxycholate, both alone and combined, significantly reduced lactase, sucrase, and maltase activity. Electron microscopic evidence showed degeneration of microvilli, disruption of mitochondrial structure, and swelling of the endoplasmic reticulum after exposure of the intestinal loops to the supernatant or deoxycholate.
 ...
PMID:Effects of an enteric anaerobic bacterial culture supernatant and deoxycholate on intestinal calcium absorption and disaccharidase activity. 197 95

Intestinal Ca2+ malabsorption has been described in spontaneously hypertensive rats (SHRs), but the molecular basis for this defect is unknown. In this study, we measured intestinal alkaline phosphatase and vitamin D-dependent Ca(2+)-binding protein (calbindin-D9k), two proteins implicated in the active pathway of intestinal Ca2+ absorption. Both proteins were measured in the small intestines of SHRs and their normotensive controls, Wistar-Kyoto rats, before, during, and after development of hypertension (4, 9, 14, 18, and 28 wk of age). At all ages, alkaline phosphatase activity in duodenum (0-6 cm) was decreased by 30-57% (P less than 0.001) and by 47-75% in the 2nd intestinal segment (6-12 cm) (P less than 0.001-0.05). Calbindin-D9k was decreased similarly. The decreases of calbindin were statistically significant (P less than 0.001-0.05) in the duodena at 4, 14, 18, and 28 wk (9-30% decreases) and in the 2nd segment at 4, 14, and 18 wk (38-69% decreases; P less than 0.001-0.005). Decreased calbindin in SHRs was documented in animals from two suppliers. The deficiencies of calbindin-D9k and alkaline phosphatase could not be attributed to malnutrition or to a generalized brush-border defect as indicated by body weights and the intestinal marker enzyme sucrase. Although calbindin-D9k was decreased in young SHRs, the serum 1,25-dihydroxycholecalciferol [1,25(OH)2D3] was increased by 59 and 129% in 4- and 9-wk-old SHRs (P less than 0.001), respectively; by contrast, serum 1,25(OH)2D3 was unchanged or decreased in older SHRs.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Intestinal vitamin D-dependent calbindin-D9k and alkaline phosphatase in spontaneously hypertensive rats. 203 38

Administration of Embelin, an experimental antifertility agent, to male rats (20 mg/kg body wt/day, daily for 15 and 30 days), caused an elevation in the uptake of D-glucose, L-alanine, L-leucine, and calcium in the small intestinal segments. An increase was also noted in the intestinal brush border membrane (BBM)-associated enzymes, sucrase, lactase, maltase, alkaline phosphatase, and leucine aminopeptidase in both the intestinal homogenates and partially purified BBM preparations, particularly after 30-day administration of the drug. Embelin treatment also caused a significant increase in the microsomal glucose-6-phosphatase and the cytosolic enzyme, lactate dehydrogenase. In the Embelin-treated animals BBM-associated total lipids, phospholipids, cholesterol, triacylglycerol, unesterified fatty acids, ganglioside-sialic acids as well as the cholesterol/phospholipids molar ratio showed a considerable increase. All these changes in the Embelin-treated animals were restored back to the normal or near normal biochemical makeup when the drug therapy was withdrawn and the animals were allowed to recover for another 15 and 30 days, respectively.
 ...
PMID:Changes in glucose/amino acid/calcium uptake and brush-border membrane-associated enzymes in rat small intestine after the administration of embelin (plant benzoquinone), an antifertility agent. 211 47

The dose relationship between medroxyprogesterone acetate (MPA), a long acting contraceptive, and rat intestinal digestive and absorptive functions has been investigated. The study revealed that the activities of brush border sucrase, lactase and leucine aminopeptidase were stimulated only at high doses, viz 70 mg/kg (180 mumol/kg) body weight and above, whereas the activity of alkaline phosphate was depressed at comparatively low dose (17.5 mg/kg; 45 mumol/kg body weight). This decrease was found to be significant (p less than 0.001) at all the doses tested. The inhibition in the intestinal uptake of calcium paralleled the decrease in alkaline phosphatase activity. Relatively high amount of MPA (140 mg/kg; 360 mumol/kg) was required to augment the uptake of glucose and amino acid. The results obtained do not indicate a close relationship between the dose of the drug and the extent of alteration in the rat intestinal digestive and absorptive functions. The study appears to confirm the association between brush border enzymes activities and uptake of nutrients in rat intestine.
 ...
PMID:Effect of various doses of medroxyprogesterone acetate on intestinal functions in rats. 230 1


<< Previous 1 2 3 4 5 6 7 8 9 Next >>