Inhibition of the sodium and potassium-stimulated adenosine triphosphatase activity during autooxidation of apomorphine

1977 ◽  
Vol 29 (1) ◽  
pp. 117-118 ◽  
Author(s):  
A. Schaefer ◽  
A. Seregi ◽  
Marta Komløs
1966 ◽  
Vol 100 (3) ◽  
pp. 762-767 ◽  
Author(s):  
N Gruener ◽  
Y Avi-Dor

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.


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