Distribution and Properties of Na+, K+-ATPase in Human Post-Mortem Kidney and the Effects of Diuretics

1972 ◽  
Vol 42 (3) ◽  
pp. 265-275 ◽  
Author(s):  
B. R. Tulloch ◽  
K. Gibson ◽  
P. Harris
Keyword(s):  
Adenosine Triphosphatase ◽  
Microsomal Fraction ◽  
Enzyme System ◽  
Post Mortem ◽  
Inhibit Activity ◽  
Adenosine Triphosphatase Activity ◽  
Diuretic Drugs ◽  
High Concentrations ◽  
Activity Dependent

1. Adenosine triphosphatase activity dependent on Mg2+ and activated by Na+ and K+ has been found in a microsomal fraction of homogenates of human postmortem kidneys. 2. Various characteristics of the enzyme system are described. 3. Activity is greater in the medulla than in the cortex. 4. Diuretic drugs inhibit activity in vitro only at high concentrations.

scholarly journals Temperature-dependence of activation and inhibition of rat-brain adenosine triphosphatase activated by sodium and potassium ions

1966 ◽  
Vol 100 (3) ◽  
pp. 762-767 ◽  
Author(s):  
N Gruener ◽  
Y Avi-Dor
Keyword(s):  
Rat Brain ◽  
Adenosine Triphosphatase ◽  
Arrhenius Plot ◽  
Enzyme System ◽  
The Other ◽  
Potassium Ions ◽  
Adenosine Triphosphatase Activity ◽  
Brain Microsomes ◽  
High Concentrations ◽  
Sodium And Potassium

1. The adenosine-triphosphatase activity of rat-brain microsomes was measured between 0 degrees and 37 degrees . The stimulatory effect of Na(+) plus K(+) on the Mg(2+)-dependent adenosine-triphosphatase activity decreased sharply with decreasing temperature and became negligible at 0 degrees . An Arrhenius plot drawn from the experimental data showed two discontinuities: one at about 6 degrees and the other at about 20 degrees . 2. The increment in activity induced by Na(+) plus K(+) was more sensitive to oligomycin at lower than at higher temperatures, but the opposite was observed for ouabain. The action of oligomycin showed a biphasic character, since below a certain concentration it caused slight activation of Na(+)-plus-K(+)-activated adenosine triphosphatase. 3. Where oligomycin increased the activity of the enzyme, it also enhanced the accumulation of an acid-precipitable phosphorylated compound formed through the transfer of the gamma-phosphate group of [(32)P]ATP to the enzyme system. Stimulatory concentrations of oligomycin did not interfere with K(+)-mediated dephosphorylation of the intermediate, though high concentrations of oligomycin counteracted the effect of K(+). 4. The temperature profile of K(+)-stimulated microsomal phosphatase qualitatively resembled that of microsomal adenosine triphosphatase.

Biosynthesis of Nitrogenous Phospholipids in Spinach Leaves

1974 ◽  
Vol 52 (6) ◽  
pp. 469-482 ◽  
Author(s):  
M. O. Marshall ◽  
M. Kates
Keyword(s):  
Microsomal Fraction ◽  
Enzyme System ◽  
Supernatant Fraction ◽  
Exchange Reactions ◽  
Methylation Pathway ◽  
Ethanolamine Kinase ◽  
Spinach Leaves

Pathways for biosynthesis of phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), in spinach leaves have been studied both in vivo (whole leaves and leaf slices) and in vitro (cell-free leaf fractions). Biosynthesis of PS was shown to occur by the action of a particle-bound CDP-diglyceride: serine phosphatidyltransferase, and PE by the action of a PS-decarboxylase localized in the 100 000 × g supernatant fraction. PE was also formed by the operation of the CDP-ethanolamine:diglyceride phosphorylethanolamine transferase, localized in the microsomal fraction. The presence of ethanolamine kinase required for formation of phosphorylethanolamine was demonstrated in vitro, but not the presence of CTP:phosphorylethanolamine cytidyltransferase; however, the latter is presumed present on the basis of in vivo results. Operation of the methylation pathway for biosynthesis of PC was established in vivo, and direct methylation of phosphatidyl-N-methylethanolamine to phosphatidyl-N,N-dimethylethanolamine (PE-diMe) and of PE-diME to PC by S-adenosylmethionine was demonstrated with a particulate enzyme system localized in the microsomal fraction; direct methylation of PE itself could not be shown in this system. PC was also synthesized by the CDP-choline:diglyceride phosphorylcholine transferase system localized in the microsomal fraction. Synthesis of PE and PC by Ca2+-stimulated exchange reactions with ethanolamine and choline, respectively, could be demonstrated, but at low rates. However, no synthesis of PS by exchange reactions with serine could be detected.

Conversion of Flavanone to Flavone, Dihydroflavonol and Flavonol with an Enzyme System from Cell Cultures of Parsley

1981 ◽  
Vol 36 (9-10) ◽  
pp. 742-750 ◽  
Author(s):  
L. Britsch ◽  
W. Heller ◽  
H. Grisebach
Keyword(s):  
Microsomal Fraction ◽  
Specific Activity ◽  
Enzyme System ◽  
High Specific Activity ◽  
Cell Suspension Cultures ◽  
Soluble Enzyme ◽  
Enzyme Preparations ◽  
Malonyl Coa ◽  
In Vitro Biosynthesis

Abstract Soluble enzyme preparations from irradiated cell suspension cultures of parsley (Petroselinum hortense Hoffm.) catalyse the conversion of flavanone to flavone, dihydroflavonol and flavonol. These reactions require 2-oxoglutarate, Fe2+ and ascorbate as cofactors. In the presence of these cofactors conversion of dihydroflavonol to flavonol was also observed. With this system in vitro biosynthesis of radioactive flavone, dihydroflavonol and flavonol from [2-14C]malonyl-CoA and 4-coumaroyl-CoA in good yield and with high specific activity is possible.We postulate that synthesis of flavone and flavonol from flavanone proceeds via 2-hydroxy-and 2,3-dihydroxyflavanone, respectively, with subsequent dehydration.The microsomal fraction of the parsley cells contains an NADPH-dependent flavanone 3'-hydroxylase.

Rabbit myocardial membrane Ca2+-adenosine triphosphatase activity: Stimulation in vitro by thyroid hormone

1984 ◽  
Vol 229 (1) ◽  
pp. 379-385 ◽  
Author(s):  
Ann Rudinger ◽  
Kathleen M. Mylotte ◽  
Paul J. Davis ◽  
Faith B. Davis ◽  
Susan D. Blas
Keyword(s):  
Thyroid Hormone ◽  
Adenosine Triphosphatase ◽  
Adenosine Triphosphatase Activity ◽  
Myocardial Membrane
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