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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)

Permeability of hepatocyte cell membrane was studied from the release into blood of hepatospecific enzymes and from 5'-nucleotidase activity in plasma membranes. A study was also made of membrane permeability of mitochondria, lysosomes and microsomes in liver cells of burnt rats from the level of non-sedimented activity and activity of malate dehydrogenase, succinate dehydrogenase, cathepsin D and glucose-6-phosphatase in appropriate organelles. Permeability of cell and lysosomal membranes was demonstrated to be disordered within the first hours after burn. One day after burn generalized disturbance of membrane permeability in the cell was observed, followed by the release into cytosol of organelles template enzymes and a decrease in the activity of membrane-bound enzymes in these organelles. The alterations persisted during 7 days of observation.
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PMID:[Structural and enzymatic disorganization of biological membranes in rat liver cells in thermal burns]. 631 92

Prolactin proteolysis by rat pituitary homogenates was assayed by measuring the release of trichloroacetic acid-soluble peptides from 125I-labelled rat prolactin. There was a distinct optimum at pH 4.3, with only trace amounts of activity at neutral and alkaline pH. Rat pituitary homogenates were subjected to analytical subcellular fractionation by sucrose density gradient centrifugation in a Beaufay automatic zonal rotor. The principal organelles were characterized by their respective marker enzymes, including: cytosol (lactate dehydrogenase); plasma membrane (5'-nucleotidase); lysosomes (N-acetyl-beta-glucosaminidase, beta-glucuronidase); mitochondria (particulate malate dehydrogenase); endoplasmic reticulum (neutral alpha-glucosidase); prolactin granules (radioimmunoassayable prolactin). Acid prolactin protease had a similar distribution to the lysosomal marker enzymes. A localisation of the activity to lysosomes was confirmed by subcellular fractionation experiments in which the lysosomes were selectively disrupted with low concentrations of the membrane perturbant, digitonin. Experiments with specific inhibitors of the lysosomal cathepsins indicate that both cathepsins B and D are implicated in pituitary prolactin proteolysis.
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PMID:Analytical subcellular fractionation of rat pituitary homogenates, with special reference to prolactin proteolysis by lysosomes. 729 6

Analytical subcellular fractionation techniques using metrizamide density gradients have been used to investigate the properties of the gut hormone storage granules and the principal organelles from homogenates of normal human jejunal mucosa obtained by peroral mucosal biopsy. The individual hormones, detected by radioimmunoassay, each showed single discrete peaks in the density gradient experiments indicating localisation to single granules each with characteristic modal densities. Thus motilin showed a modal density of 1.15, gastrin 1.16, gastric inhibitory polypeptide (GIP) 1.17, enteroglucagon 1.18 and somatostatin and vasoactive intestinal peptide (VIP) 1.10 g/ml. The following organelles, characterised by their marker enzymes were located in the density gradients; plasma membrane (5'-nucleotidase) brush border (alpha-glucosidase, pH 6.0) mitochondria (particulate malate dehydrogenase), peroxisomes (catalase), lysosomes (N-acetyl-beta-glucosaminidase), endoplasmic reticulum (alpha-glucosidase, pH 8.0), cytosol (lactate dehydrogenase). These studies provide biochemical evidence of the distinct nature of the individual gut hormone storage granules and provide a basis for studying dynamic changes in the granules in response to physiological stimuli and pathological processes.
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PMID:Characterisation of gut hormone storage granules from normal human jejunum using metrizamide density gradients. 730 92

A method for the isolation and purification of plasma membranes of Dictyostelium discoideum by equilibrium centrifugation on sucrose followed by Renografin continuous density gradients has been developed and monitored both with electron microscopy and a number of enzyme assays. On electron microscopy, the final plasma membrane fractions are judged to be freethe basis of of nuclei, rough endoplasmic reticulum, lysosomes and peroxisomes. Some profiles of the mitochondrial inner membranes are found within the plasma membrane fractions, but this contamination has been estimated to be only 5%. On the basis on enzyme assays, the plasma membrane fractions contain all the 5'-nucleotidase activity in the final gradients and are free of catalase, acid phosphatase and malate dehydrogenase activity (markers for peroxisomes, lysosomes, soluble enzymes and the matrix of mitochondria). Their content of glucose-6-phosphatase is reduced by more than 70%. The large majority of RNA and DNA have been removed from the preparation.
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PMID:The involvement of the plasma membrane in the development of Dictyostelium discoideum. I. Purification of the plasma membrane. 1625 Mar 37

Compared to the group I chaperonins such as Escherichia coli GroEL, which facilitate protein folding, many aspects of the functional mechanism of archaeal group II chaperonins are still unclear. Here, we show that monomeric forms of archaeal group II chaperonin alpha and beta from Thermoplasma acidophilum may be purified stably and that these monomers display a strong AMPase activity in the presence of divalent ions, especially Co(2+) ion, in addition to ATPase and ADPase activities. Furthermore, other nucleoside phosphates (guanosine, cytidine, uridine, and inosine phosphates) in addition to adenine nucleotides were hydrolyzed. From analyses of the products of hydrolysis using HPLC, it was revealed that the monomeric chaperonin successively hydrolyzed the phosphoanhydride and phosphoester bonds of ATP in the order of gamma to alpha. This activity was strongly suppressed by point mutation of specific essential aspartic acid residues. Although these archaeal monomeric chaperonins did not alter the refolding of MDH, their novel versatile nucleotide hydrolysis activity might fulfill a new function. Western blot experiments demonstrated that the monomeric chaperonin subunits were also present in lysed cell extracts of T. acidophilum, and partially purified native monomer displayed Co(2+)-dependent AMPase activity.
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PMID:A potentially versatile nucleotide hydrolysis activity of group II chaperonin monomers from Thermoplasma acidophilum. 1972 44


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