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)

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


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