ISSN:
1432-2013
Keywords:
Adenosine Triphosphatase
;
Plasma Membrane Enriched Fraction
;
Microsomes
;
Kidney
;
ATPase
;
zellmembranangereicherte Fraktion
;
Mikrosomen
;
Niere
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary A fraction enriched with plasma cell membranes (PMF) was isolated from rat kidney homogenate by differential centrifugation. Before NaJ treatment electron micrographs of the preparation showed a membraneous fraction with only a small contamination of mitochondria. After treatment with NaJ the residual PMF exhibited a low microsomal glucose 6-phosphatase activity. Marker enzymes of other subcellular fractions were not detected. The NaJ extracted PMF revealed a high specific activity of ATPase, 91% of which was stimulated by Na+ and K+. The MgNaK-ATPase was characterized by Michaelis Menten kinetics. In contrast, Hill coefficients (“n”) of NaK-ATPase for the activation by Na+, K+ and Mg-ATP were greater than one. Experiments with various nucleotide tri-, di- and monophosphates revealed a high substrate specificity of the NaK-ATPase. The pH optimum was in the range of 7.2. SH-reagents and ouabain depressed the Na+ and K+ stimulated enzyme activity. PMF isolated from rat kidneys exhibited an acylphosphatase and a nitrophenylphosphatase activity, both of which were stimulated by K+. Furthermore 5′-nucleotidase and leucine aminopeptidase activities were present in the fraction.—Thus, NaK-ATPase of the PMF revealed the typical properties of the NaK-ATPase demonstrated in the microsomal preparations, which has been referred to by Skou (1965) as the enzymatic basis of active cation transport.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00587793
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