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)

Extraction of pig intestinal brush border membranes with the zwitterionic detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (Chaps) in the presence of 0.5 M KCl yielded a solution which contained 60-70% of the receptor for the Escherichia coli heat-stable enterotoxin (STa) and of the Lubrol PX-activated guanylate cyclase activity present in the membrane. When the supernatant solution was diluted fivefold with 10 mM Hepes buffer (pH 7.4) and kept at 4 degrees C overnight, a precipitate formed. Centrifugation yielded a pellet (P2) which contained 25-30% of both the cyclase and the receptor in the original membranes, with a 2.5- to 3-fold enrichment of both. The process could be repeated for further enrichment (P4). The addition of MgCl2 to the diluted extract affected both basal and STa-stimulated activity of P2; 1 mM was optimal. P2 resembled membranes with respect to competitive inhibition of 125I-STa binding by STa, and the concentration-dependent activation of cyclase by STa. Guanylate cyclase in resolubilized P2 was also activated by STa. Most of the enzymes interfering with guanylate cyclase determinations were removed, as were the brush border marker enzymes sucrase and gamma-glutamyltransferase, and a GTP-binding protein that is a pertussis toxin substrate. Specific cross-linking of 125I-STa to receptors in the membrane was preserved in P2 and P4, the three proteins showing the strongest radioactivity having relative molecular masses of 55,000-60,000, 70,000-80,000, and 135,000-140,000. P2 and P4 appear to contain a complex of membrane proteins with certain functional properties intact.
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PMID:Solubilization and reprecipitation from intestinal brush border membranes of a complex containing guanylate cyclase activatable by the heat-stable enterotoxin. 168 84

Brush-border and basal-lateral membranes were prepared from rabbit intestinal epithelial cells by differential centrifugation and MgCl2 precipitation. The ADP-ribosylation of proteins in these fractions when incubated with [adenylate-32P]NAD+ and cholera toxin was investigated. Three proteins of molecular mass 45, 40 and 37 kDa were labelled in a toxin-dependent manner in each membrane fraction. The incorporation of 32P-labelled ADP-ribose was 18-fold greater in brush-border membranes than in basal-lateral membranes, comparable to the enrichment of sucrase (marker enzyme for the brush border) in these membranes. There was a 20% release of the 40 and 45 kDa proteins from the brush-border membrane following this ADP-ribosylation. Activation of adenylate cyclase by both cholera toxin and sodium fluoride was 2.7- and 2.3-fold greater, respectively, in basal-lateral membranes than in brush-border membranes, comparable to the enrichment of Na+/K+-ATPase (marker enzyme for the basal-lateral membrane) in these membranes. The effect of sodium fluoride on membranes pretreated with cholera toxin revealed no increase in adenylate cyclase activity above that due to the toxin. This presumably means that both toxin and fluoride activate adenylate cyclase by the same regulatory protein. The results show that cholera toxin catalyzes the ADP-ribosylation of regulatory proteins in the brush-border membrane, and these proteins then migrate to the basal-lateral membrane where they activate the catalytic component of adenylate cyclase.
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PMID:The activation of rabbit intestinal adenylate cyclase by cholera toxin. 260 57

The catabolic, NAD-specific glutamate dehydrogenase (NAD-GDH) of Neurospora crassa is under carbon catabolite repression. Cells grown on a glycolytic carbon source, such as sucrose, have low basal levels of enzyme activity. Treatment of repressed cells with either polymyxin B or amphotericin B resulted in derepression of NAD-GDH. Derepression at the transcriptional level occurred very rapidly (within 30 min) in response to polymyxin B addition but reached a plateau within 2 h. Amphotericin B-induced derepression initiated more slowly but continued for at least 6 h, resulting in a specific activity comparable to that seen with cells transferred to glutamate as the sole carbon source. These antibiotics had no significant effect upon the activities of two constitutive enzymes, pyruvate kinase and malate dehydrogenase. Curiously, only polymyxin B treatment derepressed invertase, another catabolite-repressed enzyme. The addition of 100 mM KCl to the growth medium blocked derepression by both antibiotics, but the addition of 50 mM MgCl2 only annulled derepression by polymyxin B. The ergosterol-deficient erg-1 mutant, which is resistant to amphotericin B, did not derepress NAD-GDH when treated with this drug. These results are consistent with derepression resulting from interactions of these antibiotics with the plasma membrane.
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PMID:Antibiotic-induced derepression of the NAD-specific glutamate dehydrogenase of Neurospora crassa. 282 59

Brush-border membranes were isolated from rabbit small intestine by procedures involving precipitation of undesired membranes with either 10 mM MgCl2 or 10 mM CaCl2. The membranes were compared on the basis of marker enzyme content and lipid composition. Ca2+-prepared membranes displayed a greater enrichment of alkaline phosphatase and sucrase activity compared to homogenate than did the Mg2+-prepared membranes. The former also displayed an impoverishment of (Na+ + K+)-ATPase activity, the specific activity of which increased several-fold in Mg2+-prepared membranes. Membranes prepared with Ca2+ were characterized by a lower phosphoacylglycerol-protein ratio and a higher phosphatidylethanolamine-phosphatidylcholine ratio. Although lysophosphoacylglycerols accounted for about 6% of the total phospholipids in these membranes compared to 2% in Mg2+-prepared membranes, the free fatty acid content was similar in both types of membranes. It was concluded that Ca2+ prepared membranes were less contaminated by basolateral membranes than were Mg2+-prepared membranes and the use of Ca2+ did not notably enhance degradation of endogenous lipids by brush-border membrane phospholipase A.
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PMID:A comparison of brush-border membranes prepared from rabbit small intestine by procedures involving Ca2+ and Mg2+ precipitation. 300 39

Neutral and alkaline invertase were identified in cells of a suspension culture of carrot (Daucus carota L.) and purified to electrophoretic homogeneity. Neutral invertase is an octamer with a molecular mass of 456 kD and subunits of 57 kD, whereas alkaline invertase is a tetramer with a molecular mass of 504 kD and subunits of 126 kD. Both enzymes had sharp pH profiles, with maximal activities at pH 6.8 for neutral invertase and pH 8.0 for alkaline invertase, and both hydrolyzed sucrose with typical hyperbolic kinetics and similar Km values of about 20 mM at pH 7.5. Neutral invertase also hydrolyzed raffinose and stachyose and, therefore, is a beta-fructofuranosidase. In contrast, alkaline invertase was highly specific for sucrose. Fructose acted as a competitive inhibitor of both enzymes, with Ki values of about 15 mM. Glucose was a noncompetitive inhibitor of both neutral and alkaline invertase, with a Ki of about 30 mM. Neither enzyme was inhibited by HgCl2. Alkaline invertase was markedly inhibited by CaCl2, MgCl2, and MnCl2, and neutral invertase was not. In contrast to alkaline invertase, neutral invertase was inhibited by the nucleotides ATP, CTP, GTP, and UTP.
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PMID:Purification and characterization of neutral and alkaline invertase from carrot. 897 97

Sugarcane neutral invertase (SNI) has been partially purified from mature sugarcane stem tissue to remove any potential competing activity. The enzyme is non-glycosylated and exhibits catalytic activity as a monomer, dimer and tetramer, most of the activity elutes as a monomer of native M(r) ca 60 k. The enzyme displays typical hyperbolic saturation kinetics for Suc hydrolysis. It has a K(m) of 9.8 mM for Suc and a pH optimum of 7.2. An Arrhenius plot shows the energy of activation of the enzyme for Suc to be 62.5 kJ mol-1 below 30 degrees and -11.6 kJ mol-1 above 30 degrees. SNI is inhibited by its products, with Fru being a more effective inhibitor than Glc. SNI is significantly inhibited by HgCl2, AgNO3, ZnCl2, CuSO4 and CoCl2 but not by CaCl2, MgCl2 or MnCl2. SNI showed no significant hydrolysis of cellobiose or trehalose.
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PMID:Partial purification and characterisation of sugarcane neutral invertase. 977 90

Invertase was purified from rose (Fructus cynosbati) hips by ammonium sulfate fractionation and hydroxyapatite column chromatography. The enzyme was obtained with a yield of 4.25% and about 10.48-fold purification and had a specific activity of 8.59 U/mg protein. The molecular mass of invertase was estimated to be 66.51 kDa by PAGE and 34 kDa by SDS-PAGE, indicating that the native enzyme was a homodimer. The enzyme was a glycoprotein and contained 5.86% carbohydrate. The K(m) for sucrose was 14.55 mM and the optimum pH and temperature of the enzyme were 4.5 and 40 degrees C, respectively. Sucrose was the most preferred substrate of the enzyme. The enzyme also hydrolyzed D(+) raffinose, D(+) trehalose and inulin (activity 39.88, 8.12 and 4.94%, respectively of that of sucrose), while D(+) lactose, cellobiose and D(+) maltose showed no effect on the enzyme. The substrate specificity was consistent with that for a beta-fructofuranoside, which is the most popular type in the higher plants. The enzyme was completely inhibited by HgCl2, MnCl2, MnSO4, FeCl3, Pb(NO3)2, ammonium heptamolybdate, iodoacetamide and pyridoxine hydrochloride. It was also inhibited by Ba(NO3)2 (86.32%), NH4Cl (84.91%), MgCl2 (74.45%), urea (71.63%), I2 (69.64%), LiCl (64.99%), BaCl2 (50.30%), Mg(NO3)2 (49.90%), CrCl3 (31.90%) and CuSO4 (21.45%) and but was activated by Tris (73.99%) and methionine (12.47%).
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PMID:Purification and some properties of rose (Fructus cynosbati) hips invertase. 2265 8