Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationship between adenylate cyclase activity in the synaptic membrane fraction (M1) of rat brain and lipid peroxidation of these membranes was examined. In the presence of 5 mM dithiothreitol (DTT), 1 to 10 microM Fe/+ activated adenylate cyclase 2- to 4-fold. Of several metal ions, Fe2+ was the most effective. Other enzymes in M1, such as Mg2+-ATPase, (Na+-K+)-ATPase, 5'-nucleotidase, acetylcholinesterase, and phosphodiesterase, were not activated by Fe2+ plus DTT. Activation of adenylate cyclase by Fe2+ plus DTT was accompanied by production of malondialdehyde, a product of lipid peroxidation. Formation of malondialdehyde was completely parallel with enzyme activation. Ascorbic acid or a NADPH system also stimulated enzyme activity and caused lipid peroxidation. Activation of the enzyme and lipid peroxidation induced by Fe2+ plus DTT, ascorbic acid, or NADPH was completely prevented by simultaneous addition of N,N'-diphenyl-p-phenylenediamine, an inhibitor of lipid peroxidation. This inhibitor also prevented the decrease in turbidity of the enzyme preparation induced by Fe2+ plus DTT. The stimulatory effects of NaF, guanylyl-5'-imidodiphosphate and calmodulin, respectively, and that of Fe2+ plus DTT on the enzyme activity were additive. Activation of adenylate cyclase by Fe2+ plus DTT was only observed in brain synaptic membranes, not in erythrocyte ghosts, liver plasma membranes, or cardiac sarcolemma. These results indicate that lipid peroxidation of synaptic membranes was accompanied by specific stimulation of adenylate cyclase activity.
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PMID:Activation of adenylate cyclase of rat brain by lipid peroxidation. 721 51

We studied copper uptake from copper dihistidine complexes by plasma membrane vesicles isolated from rat liver and compared the data with those for uptake under the same conditions by hepatocytes cultured from rat liver to determine whether membrane vesicles can be used to study copper uptake. Marker enzyme analysis showed a 28-fold increase in 5'-nucleotidase activity, a slight increase in endoplasmic reticulum and no contamination with mitochondrial membranes. Copper uptake by vesicles is temperature dependent, and solubilization with Triton X-100 results in a loss of accumulative capacity. Increasing osmotic pressure resulted in a decrease in copper levels in the vesicles at equilibrium, showing that uptake--as opposed to binding by the vesicles--occurred. Uptake by vesicles is concentration dependent, with evidence for cooperation in the uptake sites. The substrate concentration yielding 10% maximum uptake was 4.01 +/- 0.5 mumol/L, maximum uptake was 10.8 +/- 0.4 nmol/Cu/mg protein.min and the n value was 1.5 +/- 0.2. In contrast, uptake by cells showed no cooperation (n = 1.09 +/- 0.06) and a significantly higher apparent Michaelis-Menten constant (17.4 +/- 1.3 mumol/L). As expected, the maximum uptake was lower in the hepatocytes (1.82 +/- 0.08 nmol/mg protein.min). Albumin, N-ethylmaleimide and zinc all inhibited uptake in vesicles and in hepatocytes, and the degrees of inhibition were similar in both types of preparation. Vitamin C stimulated uptake in both vesicles and hepatocytes; again, there was a correlation between the increase in uptake at different concentrations. However, cadmium inhibited uptake and nickel stimulated uptake in vesicles and neither metal had any effect in hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A comparison of copper uptake by liver plasma membrane vesicles and uptake by isolated cultured rat hepatocytes. 792 4