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

A membrane preparation was obtained from rat striated muscle. The preparation used has been shown to contain plasma membranes by electron microscopy as well as by enrichment in specific activity of both a plasma membrane enzyme "marker" (5'-nucleotidase) and cell surface 125I-incorporated radioactivity. The characteristics of 125I-insulin binding to this striated muscle preparation were studied, and it was found that 125I-insulin readily and specifically binds to this membrane preparation. The binding reaction was time, pH, and temperature dependent with optimal steady-state binding conditions occurring at 20 degrees C and at pH 7.6. Under these conditions (20 degrees C, pH 7.6) skeletal muscle plasma membranes displayed little ability to degrade insulin. Binding of 125I-insulin was readily inhibited at physiologic concentrations of unlabeled insulin and the specificity of this receptor for insulin was demonstrated by finding that high concentrations of glucagon, b-LH, b-FSH, p-PRL, hCG, TSH, and HGH were without effect on 125I-insulin binding and that insulin analogues inhibited binding in proportion to their biologic activity. When membranes from older, fatter rats were compared to membranes from younger, lean animals, 5'-nucleotidase specific activity and insulin degrading activity were found to be comparable. On the other hand, insulin binding to membrane receptors was decreased 30%-40% in the older, fatter animals. Thus, these studies indicate that (1) specific insulin receptors exist in skeletal muscle plasma membranes, and (2) membranes from older, fatter rats have fewer receptors than those from younger, lean animals.
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PMID:Insulin receptors of skeletal muscle: specific insulin binding sites and demonstration of decreased numbers of sites in obese rats. 0 34

A concomitant increase in the activity of LH-senstive adenylate cyclase and in the number of LH/hCG binding sites was induced in ovaries of immature rats upon administration of pregnant mare serum gonadotropin (PMSG), a hormone preparation known to have predominantly follicle stimulation (FSH-like) activity. When an optimal dose of PMSG (15 i.u./rat) was administered to 25-day-old rats, specific activity of LH-dependent adenylate cyclase and the number of binding sites for LH/hCG per mg protein remained unchanged during the first 24h, but 48h after injection a 2-to 4-fold increase in both parameters was observed. By contrast, there was no change in basal adenylate cyclase activity or in the response of the enzyme to the stimulatory action of guanosine-5'-(beta gamma-imino) triphosphate (Gpp (NH)p), GTP, or NaF. Specific activity of succinate cytochrome c reductase, glucose-6-phosphatase and 5'-nucleotidase were found to be unaffected by the hormonal pretreatment, although total protein determined in these homogenates increased 3-fold in the course of this treatment. It is inferred that during follicular maturation, FSH enhances the responsiveness of ovarian adenylate cyclase to LH by stimulating the insertion of LH/hCG-receptors into the cell membrane.
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PMID:Synchronous generation of ovarian hCG binding sites and LH-sensitive adenylate cyclase in immature rats following treatment with pregnant mare serum gonadotropin. 19 42

A method is reported for preparing surface (plasma) membranes from rat Sertoli cells. The procedure is based upon homogenization in hypotonic buffer, extraction in a two-phase system, and sedimentation through two sucrose density gradients. The purified membranes consist of large sheets of membrane. The identity and purity of the membranes was demonstrated by electron microscopy, enzyme markers, and functional activities associated with the membranes (binding of follicle-stimulating hormone [FSH] and production of cyclic adenosine 5'-monophosphate [cAMP]. Electron microscopy showed membranes with small fragments of cytoplasm attached to the inside of the membrane sheets. Marker enzymes for plasma membrane (5'-nucleotidase and alkaline phosphatase) showed more than 16- and 6-fold enrichment, respectively, and other enzymes showed that contamination by nuclei, mitochondria, endoplasmic reticulum, or cytosol was negligible. Binding of FSH was found to be specific, with KD 1.2 nM and the equivalent of 7500 sites per cell. This binding was enriched 20-fold compared to whole homogenate. Production of cAMP by membranes was increased by addition of FSH and by forskolin to the purified membranes in vitro.
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PMID:Plasma membranes from rat Sertoli cells: purification and properties. 310 2

Various intracellular organelles as well as outer cell membranes of bovine corpora lutea intrinsically contain gonadotropin receptors (Rao et al., J biol chem 256 (1981) 2628 [5]). In order to investigate whether exogenously added human choriogonadotropin (hCG) can internalize and bind to the intracellular sites, bovine luteal slices that had been carefully checked with respect to structural and functional integrity were incubated with 0.1 nM 125I-hCG. Following incubation, specific radioactivity was found to be associated with various intracellular organelles, but not with cytosol. The order of radioactivity uptake by subcellular organelles following a 2-h incubation was: Golgi medium greater than Golgi heavy greater than Golgi light greater than plasma membranes = rough endoplasmic reticulum greater than mitochondria-lysosomes- greater than nuclei. The 5'-nucleotidase activity and electron microscopic examination of the fractions revealed that the presence of radioactivity in the intracellular organelles cannot be attributed solely to plasma membrane contamination. The internalization and intracellular binding of 125I-hCG was time and temperature-dependent. Only excess unlabeled hCG and hLH (but not hCG subunits, FSH and PRL) competed with 125I-hCG for internalization in luteal slices. Very little or no 125I-hCG added was internalized in liver or kidney slices; luteal, liver and kidney slices accumulated neither 125I-BSA nor 125I. The radioactivity eluted from various luteal subcellular organelles was able to rebind to fresh corresponding organelles and came off Sepharose 6B columns in a position corresponding to native 125I-hCG. The gel filtration profile of detergent-solubilized radioactivity revealed that 125I-hCG was macromolecular bound. The degraded and altered 125I-hCG was found in the incubation media.
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PMID:Internalization of 125I-human choriogonadotropin in bovine luteal slices. A biochemical study. 670 37