scholarly journals Phosphomonoesterase hydrolysis of polyphosphoinositides in rat kidney: Properties and subcellular localization of the enzyme system

1975 ◽  
Vol 150 (3) ◽  
pp. 537-551 ◽  
Author(s):  
P H Cooper ◽  
J N Hawthorne
Keyword(s):  
Phosphatase Activity ◽  
Metal Ion ◽  
Rat Kidney ◽  
Gradient Centrifugation ◽  
Sodium Deoxycholate ◽  
Subcellular Fractionation ◽  
Kidney Cortex ◽  
Ph Optimum ◽  
Triton X ◽  
Hydrolysis Of

Tthe properties of diphosphoinositide and triphosphoinositide phosphatases from rat kidney homogenate were studied in an assay system in which non-specific phosphatase activity was eliminated. The enzymes were not completely metal-ion dependent and were activated by Mg2+. The detergent sodium deoxycholate, Triton X-100 and Cutscum inhibited the reaction; cetyltrimethylammonium bromide only activated when added with the subtrates and in the presence Mg2+. Both enzymes had a pH optimum of 7.5. Ca2+ and Li+ both activated triphosphoinositide phosphatase, but Ca2+ inhibited and L+ had little effect on diphosphoinositide phosphatase. Cyclic AMP had no effect on either enzyme. The enzymes were three times more active in kidney cortex than in the medulla. On subcellular fractionation of kidney-cortex homogenates by differential and density-gradient centrifugation, the distribution of the enzymes resembled that of thiamin pyrophosphatase (assayed in the absence of ATP), suggesting localization in the Golgi complex. However, the distribution differed from that of the liver Golgimarker galactosyltransferase. Activities of both diphosphoinositide and triphosphoinositide phosphatases and thiamin pyrophosphatase were low in purified brush-border fragments. Further experiments indicate that at least part of the phosphatase activity is soluble.

scholarly journals Characterization of calcium-ion-activated adenosine triphosphatase in the plasma membrane of rat mast cells

1976 ◽  
Vol 156 (3) ◽  
pp. 691-700 ◽  
Author(s):  
P H Cooper ◽  
D R Stanworth
Keyword(s):  
Plasma Membrane ◽  
Mast Cells ◽  
Adenosine Triphosphatase ◽  
Gradient Centrifugation ◽  
Subcellular Fractionation ◽  
Ph Optimum ◽  
Peritoneal Mast Cells ◽  
Triton X ◽  
Calcium Ion Activated

The properties of a Ca2+ activated adenosine triphosphatase shown to be present in homogenates of purified rat peritoneal mast cells were investigated. The enzyme was activated by Ca2+, Mg2+, and to a lesser extent by Mn2+ and Co2+. Ca2+ alone was necessary for full activity and the further addition of Mg2+ did not have any effect. The chelating agents EGTA (ethanedioxybis(ethylamine)tetra-acetate) and EDTA completely inhibited the reaction. The pH optimum was 7.8. Reduced glutathione, cysteine, dithiothreitol, N-ethylmaleimide, urea, ADP, NaF, increasing ionic strength and Triton X-100 all inhibited the reaction. On subcellular fractionation of mast-cell homogenates by density-gradient centrifugation, the distribution of Ca2+ activated adenosine triphosphatase resembled that of 5′-nucleotidase, but differed from that of the other markers used, suggesting localization in the plasma membrane. Further experiments indicated that the enzyme is present on the external surface of the plasma membrane.

scholarly journals d-myoInositol 1:2-cyclic phosphate 2-phosphohydrolase

1972 ◽  
Vol 127 (1) ◽  
pp. 113-118 ◽  
Author(s):  
R. M. C. Dawson ◽  
N. Clarke
Keyword(s):  
Small Intestine ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Ph Optimum ◽  
Rat Kidney Cortex ◽  
Mammalian Tissues ◽  
Cyclic Phosphate ◽  
Hydrolysis Of

1. An enzyme in extracts of mammalian tissues catalyses the hydrolysis of d-myoinositol 1:2-cyclic phosphate (an intermediary in the enzymic degradation of phosphatidylinositol) to produce d-myoinositol 1-phosphate. 2. The enantiomorph of the substrate is not attacked. 3. The pH optimum is about 8.1–8.3 and the reaction is stimulated by Mg2+ ions. 4. Extracts from rat kidney cortex and medulla are very rich sources of the enzyme; brain, testis and small intestine contain intermediary activities, and other tissues contain very small amounts.

The β-glucosidases of porcine kidney

1977 ◽  
Vol 55 (2) ◽  
pp. 140-145 ◽  
Author(s):  
Julian N. Kanfer ◽  
Richard A. Mumford ◽  
Srinivasa S. Raghavan
Keyword(s):  
Sodium Taurocholate ◽  
Hydrolytic Activity ◽  
Acidic Ph ◽  
Porcine Kidney ◽  
Ph Optimum ◽  
Pig Kidney ◽  
Competitive Inhibitors ◽  
Triton X ◽  
Hydrolysis Of ◽  
Estradiol 17Β

Some of the properties of a partially purified particle bound and soluble β-glucosidase (EC 3.2.1.21) from pig kidney were compared. The soluble β-glucosidase (1) hydrolyzed 4-methylumbelliferyl-β-D-glucoside (4-MU-β-D-glucoside) 17α-estradiol 3β-glucoside, 17α-estradiol 17β-glucoside, and salicin, but not glucosylceramide, (2) possessed a broad pH optimum (5.5–7.0), (3) had an isoelectric point of 4.9, and (4) was inhibited by Triton X-100. Several compounds were found to be competitive inhibitors of its hydrolytic activity, gluconolactam and estrone β-glucoside being the most effective. In contrast, a particulate β-glucosidase purified from the same tissue (1) had an acidic pH optimum (5.0), (2) was stimulated by sodium taurocholate and 'Gaucher's factor' for the hydrolysis of both 4-MU-β-glucoside and glucosylceramide, and (3) was capable of catalyzing a transglucosylation reaction employing 4-MU-β-D-glucoside or glucosylceramide as the glucosyl donor, and [l4C]ceramide as acceptor.

scholarly journals Renin substrate in granules from rat kidney cortex

1976 ◽  
Vol 154 (3) ◽  
pp. 625-637 ◽  
Author(s):  
B J. Morris ◽  
C I. Johnston
Keyword(s):  
Microsomal Fraction ◽  
Rat Kidney ◽  
Gradient Centrifugation ◽  
Rat Plasma ◽  
Reaction Scheme ◽  
Kidney Cortex ◽  
Angiotensin I ◽  
Renin Substrate ◽  
Rat Kidney Cortex ◽  
Molecular Weights

1. Subcellular fractions of rat kidney cortex generated angiotensin I continuously over 2h when incubated at 37degreesC with rat renin, indicating the presence of renin substrate within cells in the renal cortex. 2. Renin substrate was located in highest specific concentration in particulate fractions. The particles containing renin substrate had a sedimentation velocity slightly lower than mitochondria and renin granules but greater than the microsomal fraction. 3. Isopycnic gradient centrifugation indicated a density of 1.190g/ml for the particles containing renin substrate, compared with 1.201 for renin granules, 1.177 for mitochondria, and 1.170 and 1.230 for lysosomes in the heavy-granule fraction. 4. In the liver, renin substrate was also found in particles, but these had a lower sedimentation rate than those from the kidney. 5. The molecular weights of renin substrate in kidney and liver granules and rat plasma were similar, namely 61000-62000. 6. On the basis of these biochemical findings, a mechanism for the intrarenal production of angiotensin, incorporating a subcellular reaction scheme, is proposed.

scholarly journals The effect of chemical agents on the turnover of the bound phosphate associated with the sodium-and-potassium ion-stimulated adenosine triphosphatase in ox brain microsomes

1970 ◽  
Vol 120 (1) ◽  
pp. 1-13 ◽  
Author(s):  
R. Rodnight
Keyword(s):  
Sodium Chloride ◽  
Atp Hydrolysis ◽  
Sodium Dodecyl ◽  
Sodium Deoxycholate ◽  
Protein Ratio ◽  
Chemical Agents ◽  
Rapid Fall ◽  
Triton X ◽  
Hydrolysis Of ◽  
Sodium And Potassium

1. The effect of chemical agents on the turnover of the Na+-dependent bound phosphate and the simultaneous Na+-dependent hydrolysis of ATP by a membrane preparation from ox brain was studied at an ATP/protein ratio of 12.5pmol/μg. 2. The agents were added immediately after phosphorylation of the preparation in a medium containing 50mm-sodium chloride and 2.5μm-[γ-32P]ATP. 3. Concentrations of sodium chloride above 150mm, calcium chloride to 20mm and suramin to 1.4mm inhibited both phosphorylation and dephosphorylation and concomitantly slowed ATP hydrolysis. At 125mm-sodium chloride dephosphorylation and hydrolysis were slightly slowed without affecting phosphorylation. 4. Ethanol to 1.6m concentration inhibited dephosphorylation without affecting phosphorylation; the bound phosphate was increased and ATP hydrolysis slowed. 5. Ouabain to 4mm concentration partially inhibited ATP hydrolysis and caused a transient (1–2s) rise in bound phosphate followed by a rapid fall to a lower plateau value, which eventually declined to zero by the time ATP hydrolysis was complete. 6. Of the detergents examined Lubrol W, Triton X-100 and sodium deoxycholate had no significant effect on turnover. Sodium dodecyl sulphate and sodium decyl sulphate to 3.5mm and 20mm respectively completely inhibited turnover and ATP hydrolysis and stabilized the bound phosphate.

scholarly journals Phosphatidylinositol kinase and diphosphoinositide kinase of rat kidney cortex: properties and subcellular localization

1976 ◽  
Vol 160 (1) ◽  
pp. 97-105 ◽  
Author(s):  
P H Cooper ◽  
J N Hawthorne
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Brush Border ◽  
Rat Kidney ◽  
Subcellular Fractionation ◽  
Kidney Cortex ◽  
Marker Enzymes ◽  
Rat Kidney Cortex ◽  
Phosphatidylinositol Kinase ◽  
Golgi Membranes

The properties of phosphatidylinositol kinase and diphosphoinositide kinase from rat kidney cortex were studied. The enzymes were completely Mg2+-dependent. Cutscum detergent activated phosphatidylinositol kinase, but diphosphoinositide kinase was inhibited by all detergents tested. The pH optima were 7.7 for phosphatidylinositol kinase and 6.5 for diphosphoinositide kinase. On subcellular fractionation of kidney-cortex homogenates by differential centriflgation, the distribution of phosphatidylinositol kinase resembled that of the marker enzymes for brush-border, endoplasmic-reticulum and Golgi membranes. Diphosphoinositide kinase distribution resembled that of thiamin pyrophosphatase (assayed in the absence of ATP), diphosphoinositide phosphatase and triphosphoinositide phosphatase. Activities of both kinases were low in purified brush-border fragments. Diphosphoinositide kinase is probably localized in the Golgi complex.

scholarly journals Localization of d-myoinositol 1:2-cyclic phosphate 2-phosphohydrolase in rat kidney

1972 ◽  
Vol 130 (1) ◽  
pp. 229-238 ◽  
Author(s):  
N. Clarke ◽  
R. M. C. Dawson
Keyword(s):  
Alkaline Phosphatase ◽  
Rat Kidney ◽  
Gradient Centrifugation ◽  
Subcellular Fractionation ◽  
Proximal Tubules ◽  
Outer Cortex ◽  
Inositol 1 ◽  
Brush Borders ◽  
Cyclic Phosphate ◽  
Pars Convoluta

1. On subcellular fractionation of rat kidney homogenates by differential and density-gradient centrifugation, the bulk of the inositol 1:2-cyclic phosphate 2-phosphohydrolase activity remains with the alkaline phosphatase activity, suggesting localization in the brush borders of the proximal tubules. 2. Histochemical studies with a medium containing inositol 1:2-cyclic phosphate and Escherichia coli phosphomonoesterase show Gomori staining around the brush borders of the proximal tubules in the outer cortex only. 3. Serial sections across the kidney from cortex perimeter to papilla suggest that the inositol 1:2-cyclic phosphate 2-phosphohydrolase has a limited distribution along the proximal tubule of the nephron, probably being limited to the pars convoluta, whereas the alkaline phosphatase extends along the pars recta.

scholarly journals Cellular and subcellular localization of enzymes of arginine metabolism in rat kidney

1992 ◽  
Vol 282 (2) ◽  
pp. 369-375 ◽  
Author(s):  
S N Dhanakoti ◽  
M E Brosnan ◽  
G R Herzberg ◽  
J T Brosnan
Keyword(s):  
Rat Kidney ◽  
Subcellular Fractionation ◽  
Kidney Cortex ◽  
Ornithine Aminotransferase ◽  
Outer Medulla ◽  
Argininosuccinate Synthase ◽  
Distal Tubules ◽  
Convoluted Tubules ◽  
Inner Cortex ◽  
Proximal Convoluted Tubules

Rat kidneys extract citrulline derived from the intestinal metabolism of glutamine and convert it stoichiometrically into arginine. This pathway constitutes the major endogenous source of arginine. We investigated the localization of enzymes of arginine synthesis, argininosuccinate synthase and lyase, and of breakdown, arginase and ornithine aminotransferase, in five regions of rat kidney, in cortical tubule fractions and in subcellular fractions of cortex. Argininosuccinate synthase and lyase were found almost exclusively in cortex. Arginase and ornithine aminotransferase were found in inner cortex and outer medulla. Since cortical tissue primarily consists of proximal convoluted and straight tubules, distal tubules and glomeruli, we prepared cortical tubule fragments by collagenase digestion of cortices and fractionated them on a Percoll gradient. Argininosuccinate synthase and lyase were found to be markedly enriched in proximal convoluted tubules, whereas less than 10% of arginase and ornithine aminotransferase, were recovered in this fraction. Arginine production from citrulline was also enriched in proximal convoluted tubules. Subcellular fractionation of kidney cortex revealed that argininosuccinate synthase and lyase are cytosolic. We therefore conclude that arginine synthesis occurs in the cytoplasm of the cells of the proximal convoluted tubule.

scholarly journals Subcellular localization and properties of rat liver adenosine diphosphatase

1980 ◽  
Vol 192 (2) ◽  
pp. 527-535 ◽  
Author(s):  
G P Smith ◽  
G D Smith ◽  
T J Peters
Keyword(s):  
Rat Liver ◽  
Gradient Centrifugation ◽  
Intracellular Localization ◽  
Sucrose Density Gradient ◽  
Subcellular Fractionation ◽  
Single Step ◽  
Sucrose Density Gradient Centrifugation ◽  
Ph Optimum ◽  
Outer Membranes ◽  
Selective Membrane

ADPase (adenosine diphosphatase) was assayed in rat liver homogenates with [beta-32P]ADP as substrate. The activity had a pH optimum of 8.0 and was strongly activated by Mg2+. The intracellular localization was determined by analytical subcellular fractionation with single-step sucrose-density-gradient centrifugation. Selective membrane perturbants were used to enhance the resolution of the various organelles. ADPase was localized to the mitochondria. Mitochondria were isolated by differential centrifugation and subfractionated by selective disruption of the inner and outer membranes. The intramitochondrial localization of ADPase was compared with various marker enzymes and was shown to be concentrated in the outer-membrane fractions. The effects of various inhibitors on the ADPase activity were determined and the possibility that the activity could be due to known enzyme systems was considered. It is concluded that ADP degradation is due to a hitherto unrecognized mitochondrial enzyme.

scholarly journals Proteins of the kidney microvillar membrane. The amphipathic forms of endopeptidase purified from pig kidneys

1983 ◽  
Vol 211 (3) ◽  
pp. 743-753 ◽  
Author(s):  
I S Fulcher ◽  
A J Kenny
Keyword(s):  
Chelating Agents ◽  
Gel Filtration ◽  
Small Region ◽  
The Other ◽  
Kidney Cortex ◽  
Dimeric Molecule ◽  
Crossed Immunoelectrophoresis ◽  
Triton X ◽  
Hydrolysis Of ◽  
Positively Charged

The purification of detergent-solubilized kidney microvillar endopeptidase (EC 3.4.24.11) by immuno-adsorbent chromatography is described. The product (the d-form) was 270-fold purified compared with the homogenate of kidney cortex and was obtained in a yield of 5%. It was free of other peptidase activities and homogeneous by electrophoretic analyses. It contained about 15% carbohydrate and one Zn atom/subunit. Two trypsin-treated forms were also characterized. One (dt-form) was obtained by treatment of the d-form. The other (tt-form) was the result of solubilizing the membrane by treatment with toluene and trypsin. All three forms had apparent subunit Mr values of approx. 89 000, but the d-form appeared to be slightly larger than the other two. Estimates of Mr by gel filtration showed that of the tt-form to be 216 000 whereas those of the other forms were 320 000. An estimate of the detergent (Triton X-100) bound to the d- and dt-forms accounted for this difference. By several criteria, including charge-shift crossed immunoelectrophoresis and hydrophobic chromatography, the d- and dt-forms were shown to be amphipathic molecules. In contrast, the tt-form was hydrophilic in its properties. Differences in ionic properties were also noted, consistent with the loss, in the case of the dt-form, of a positively charged peptide. The results indicate that the native endopeptidase is a dimeric molecule, each subunit being anchored in the membrane by a relatively small region of the polypeptide close to one or other terminus. The d- and dt-forms had similar enzyme activity when assayed by the hydrolysis of 125I-insulin B-chain. Chelating agents and phosphoramidon inhibited the endopeptidase. The kinetic constants were determined by a new two-stage fluorimetric assay using glutarylglycylglycylphenylalanine 2-naphthylamide as substrate and aminopeptidase N (EC 3.4.11.2) to hydrolyse phenylalanine 2-naphthylamide. The Km was 68 microM and Vmax. 484nmol X min-1 X (mg of protein)-1.

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