scholarly journals A membrane-bound metallo-endopeptidase from rat kidney. Characteristics of its hydrolysis of peptide hormones and neuropeptides

1992 ◽  
Vol 204 (2) ◽  
pp. 547-552 ◽  
Author(s):  
Toru YAMAGUCHI ◽  
Hiroshi KIDO ◽  
Nobuhiko KATUNUMA
Keyword(s):  
Rat Kidney ◽  
Peptide Hormones ◽  
Membrane Bound ◽  
Hydrolysis Of

An ATP-inhibited soluble 5'-nucleotidase of rat kidney

1988 ◽  
Vol 254 (2) ◽  
pp. F191-F195
Author(s):  
M. Le Hir ◽  
U. C. Dubach
Keyword(s):  
High Speed ◽  
Catalytic Properties ◽  
Divalent Cations ◽  
Rat Kidney ◽  
Maximal Activity ◽  
Rate Of Hydrolysis ◽  
Membrane Bound ◽  
Ph Range ◽  
Hydrolysis Of

Hydrolysis of 5'-AMP by 5'-nucleotidase is a possible source of adenosine in the kidney. A renal membrane-bound ecto-5'-nucleotidase has been previously described. The present study deals with the catalytic properties of a 5'-AMP phosphohydrolase partially purified from high-speed supernatants of rat kidney homogenates. It exhibits phosphatase activity toward 5'-AMP, 5'-IMP, and 5'-GMP, but not toward 2'- and 3'-AMP and corresponds therefore to a 5'-nucleotidase. The hydrolysis of 5'-AMP by the soluble 5'-nucleotidase requires divalent cations. Maximal activity is reached with 10 microM of either Mn2+ or Co2+, whereas half-maximal activity is obtained with approximately 400 microM Mg2+. The soluble 5'-nucleotidase exhibits Michaelis-Menten kinetics with a Km of 9.5 microM for 5'-AMP. In the presence of 1 mM of free Mg2+, physiological concentrations of ATP provoke an increase of the Km for 5'-AMP and a decrease of Vmax. An increase of the pH of 0.4 units in the pH range 6.4-7.4 roughly doubles the rate of hydrolysis of 5'-AMP. The effects of ATP and of the pH are compatible with a role of the renal soluble 5'-nucleotidase in the hydrolysis of 5'-AMP and in the production of adenosine during hypoxia.

scholarly journals A comparison of d-inositol 1:2-cyclic phosphate 2-phosphohydrolase with other phosphodiesterases of kidney

1973 ◽  
Vol 134 (1) ◽  
pp. 59-67 ◽  
Author(s):  
R. M. C. Dawson ◽  
N. G. Clarke
Keyword(s):  
Guinea Pig ◽  
Rat Kidney ◽  
Kidney Tissue ◽  
Outer Cortex ◽  
Inositol 1 ◽  
Brush Borders ◽  
Straight Portion ◽  
Membrane Bound ◽  
Cyclic Phosphate ◽  
Hydrolysis Of

1. The ability to hydrolyse various phosphodiesterase substrates was examined in subcellular fractions of rat kidney and in serial slices of the kidneys of mouse, rat, guinea pig and ox cut from the cortex perimeter inwards. 2. d-Inositol 1:2-cyclic phosphate 2-phosphohydrolase could be clearly distinguished from phosphodiesterases which hydrolyse 2′:3′- and 3′:5′-cyclic AMP and p-nitrophenyl thymidine 5′-phosphate (phosphodiesterase I). The hydrolysis of sn-glycero-3-phosphorylcholine showed a distribution identical with that of particle-bound d-inositol 1:2-cyclic phosphate 2-phosphodiesterase, but there was a 30-fold difference in the ratio of enzyme activities between the rat and guinea pig. 3. In rat and mouse kidney, d-inositol 1:2-cyclic phosphate 2-phosphohydrolase is virtually all membrane bound and in the outer cortex, whereas in guinea-pig kidney the enzyme is almost entirely soluble and located throughout the kidney tissue. Some properties of the soluble enzyme are described. 4. Distribution and histochemical studies indicated that in the rat and mouse, phosphodiesterase I is associated with the brush borders of the straight portion (pars recta) of the proximal tubule, whereas inositol 1:2-cyclic phosphate 2-phosphohydrolase and probably glycerylphosphorylcholine diesterase are associated with the brush borders of the convoluted part of the tubule (pars convoluta).

Purification of a Membrane-Bound Neutral Endopeptidase from Rat Kidney and Its Activation by Polyamines

1984 ◽  
Vol 95 (6) ◽  
pp. 1725-1732 ◽  
Author(s):  
Yasuhiro WATANABE ◽  
Yoshimitsu SHIMAMORI ◽  
Masakazu OZAKI ◽  
Masahide UCHIDA ◽  
Yukio FUJIMOTO
Keyword(s):  
Rat Kidney ◽  
Neutral Endopeptidase ◽  
Membrane Bound

Insulin uptake and processing by cultured mouse glomerular endothelial cells

1993 ◽  
Vol 265 (2) ◽  
pp. C453-C459 ◽  
Author(s):  
R. Rabkin ◽  
T. Tsao ◽  
S. J. Elliot ◽  
L. J. Striker ◽  
G. E. Striker
Keyword(s):  
Endothelial Cells ◽  
High Performance ◽  
Adrenocorticotropic Hormone ◽  
Intermediate Formation ◽  
Peptide Hormones ◽  
Insulin Degradation ◽  
Glomerular Endothelial Cells ◽  
Membrane Bound ◽  
Vascular Beds ◽  
Insulin Uptake

Endothelial cells isolated from a variety of vascular beds bind and transport insulin but exhibit relatively low insulin degrading activity. Because endothelial cells exhibit heterogeneity and since kidney is a major site of insulin degradation, we studied the processing of insulin by glomerular endothelial cells (GEC). When exposed to 2 x 10(-10) M 125I-labeled insulin, GEC associated with the hormone in a specific manner. This interaction was inhibited by insulin but not by a number of unrelated peptide hormones. Over a 90-min period, GEC degraded 42 +/- 3% of the 125I-insulin, as measured by solubility in trichloroacetic acid (TCA). Degradation was inhibited 90% by an excess of insulin or adrenocorticotropic hormone (10(-6) M) and 57% by glucagon, whereas growth hormone and calcitonin were without effect. Separation of plasma membrane bound from internalized insulin was achieved by decreasing extracellular pH. In the steady state, 43% of cell-associated insulin was membrane bound and 57% internalized. The fate of the internalized 125I-insulin was examined by incubating acid-washed cells at 37 degrees C for 60 min. Over this time 18% of the radioactivity was released as TCA insoluble- and 72% as TCA-soluble radioactivity. Release was increased by insulin (10(-6) M) but not by unrelated peptide hormones. In the presence of chloroquine, 125I-insulin release increased by one third while degradation fell. High-performance liquid chromatography revealed that GEC released both intact insulin and large intermediates and that chloroquine inhibited intermediate formation.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

The (Na++K+) activated enzyme system and its relationship to transport of sodium and potassium

1974 ◽  
Vol 7 (3) ◽  
pp. 401-434 ◽  
Author(s):  
Jens Chr. Skou
Keyword(s):  
Transport System ◽  
Enzyme System ◽  
Membrane Bound ◽  
Hydrolysis Of ◽  
Sodium And Potassium

It seems to be the membrane bound (Na++K+)-activated enzyme system which transforms the energy from a hydrolysis of ATP into a vectorial movement of sodium out and potassium into the cell against electrochemical gradients, i.e. this systems seems to be the transport system for sodium and potassium (see, for example, review by Skou, 1972; Hokin & Dahl, 1972).

A Membrane-Bound Metallo-Endopeptidase from Rat Kidney: Its Immunological Characterization1

1993 ◽  
Vol 113 (3) ◽  
pp. 299-303 ◽  
Author(s):  
Tom Yamaguchi ◽  
Hiroshi Kido ◽  
Riko Kitazawa ◽  
Sohei Kitazawa ◽  
Masaaki Fukase ◽  
...  
Keyword(s):  
Rat Kidney ◽  
Membrane Bound

Arginine synthesis in mouse and rabbit nephron: localization and functional significance

1993 ◽  
Vol 264 (6) ◽  
pp. F1038-F1045 ◽  
Author(s):  
O. Levillain ◽  
A. Hus-Citharel ◽  
F. Morel ◽  
L. Bankir
Keyword(s):  
Incubation Medium ◽  
Functional Significance ◽  
Rat Kidney ◽  
Arginase Activity ◽  
Polyamine Synthesis ◽  
Main Site ◽  
Nephron Segments ◽  
Steep Decrease ◽  
Hydrolysis Of ◽  
Lower Production

In the rat kidney, arginine (Arg) synthesis is restricted to the proximal tubule with a decreasing intensity from its convoluted (PCT) to its straight part (PST). The present study was designed to investigate the pattern of Arg synthesis along the nephron in other mammals, the mouse and rabbit. Microdissected representative nephron segments were incubated with 0.1 mM L-[ureido-14C]citrulline in a sealed chamber. Addition of arginase and urease to the incubation medium led to the hydrolysis of Arg into ornithine, NH3, and 14CO2. The latter was trapped in KOH and counted (results are in fmol Arg.min-1.mm tubular length-1). As in the rat, the main site of Arg synthesis in both species was found to be the PCT (mouse, 191; and rabbit, 57). A lower production was observed in rabbit and mouse PST and in rabbit distal segments. Along the PCT (from 1st to 4th mm after the glomerulus), a steep decrease is observed in mouse (595 and 37, respectively) but not in rabbit (57 and 23). The fate of the newly synthesized Arg probably depends on its site of production. Intracellular arginase activity is known to be present in the cortical (C) and medullary (OS) PST, in both mouse and rabbit. In rabbit only, arginase activity is also found in the PCT. We observed that a large part of Arg was further hydrolyzed into urea and ornithine in CPST and OSPST of mouse (66 and 80%, respectively) and rabbit (40 and 70%) but not in rabbit PCT (8%). Thus Arg produced by PCT in both species is probably released in the cortical blood, whereas Arg produced in PST may serve locally to produce urea and ornithine, and the latter could be used for polyamine synthesis.

scholarly journals The metabolism of neuropeptides. Hydrolysis of peptides by the phosphoramidon-insensitive rat kidney enzyme ‘endopeptidase-2’ and by rat microvillar membranes

1988 ◽  
Vol 255 (1) ◽  
pp. 45-51 ◽  
Author(s):  
S L Stephenson ◽  
A J Kenny
Keyword(s):  
Substance P ◽  
Rat Kidney ◽  
Peptide Fragments ◽  
Hydrophobic Amino Acid ◽  
Prolonged Incubation ◽  
Minor Contribution ◽  
Kidney Enzyme ◽  
Hydrophobic Amino Acid Residue ◽  
A Minor ◽  
Hydrolysis Of

Endopeptidase-2, the second endopeptidase in rat kidney brush border [Kenny & Ingram (1987) Biochem. J. 245, 515-524] has been further characterized in regard to its specificity and its contribution to the hydrolysis of peptides by microvillar membrane preparations. The peptide products were identified, after incubating luliberin, substance P, bradykinin and angiotensins I, II and III with the purified enzyme. The bonds hydrolysed were those involving a hydrophobic amino acid residue, but this residue could be located at either the P1 or P1′ site. Luliberin was hydrolysed faster than other peptides tested, followed by substance P and bradykinin. Human alpha-atrial natriuretic peptide and the angiotensins were only slowly attacked. Oxytocin and [Arg8]vasopressin were not hydrolysed. No peptide fragments were detected on prolonged incubation with insulin, cytochrome c, ovalbumin and serum albumin. In comparison with pig endopeptidase-24.11 the rates for the susceptible peptides were, with the exception of luliberin, much lower for endopeptidase-2. Indeed, for bradykinin and substance P the ratio kcat./Km was two orders of magnitude lower. Since both endopeptidases are present in rat kidney microvilli, an assessment was made of the relative contributions to the hydrolysis of luliberin, bradykinin and substance P. Only for the first named was endopeptidase-2 the dominant enzyme; for bradykinin it made an equal, and for substance P a minor, contribution.

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