Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01350 (gastrin)
 9,683 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

As is the case with many other peptide hormones of the brain and intestine, the formation of biologically active gastrin from a glycine-extended processing intermediate occurs via the action of a peptidylglycyl alpha-amidating monooxygenase (PAM). The observation that gastrin exists primarily as unamidated precursors in the pituitary but as amidated gastrin in the antrum prompted this study to examine whether the amidating enzymes in the two organs were different in their characteristics. Amidating activity was quantified by measuring the conversion of glycine-extended tridecagastrin (G13-Gly) to amidated tridecagastrin and glycine-extended hexapancreatic polypeptide (PP6-Gly) to amidated hexapancreatic polypeptide by radio-immunoassay. Two molecular forms of amidating activity were identified in both the porcine antrum and pituitary. The first, PAM-A, had an apparent Mr of 51,000 and a net negative charge at pH 7.0, whereas PAM-B was smaller (Mr approximately 30,000) and had a net positive charge at pH 7.0. Both molecular forms were similar in their cofactor requirements (copper, ascorbic acid, and catalase) and pH optima in the antrum and pituitary. The Km was significantly lower and the Vmax higher for PP6-Gly than for G13-Gly in the pituitary and antrum. These data suggest that although there is no difference between antral and pituitary PAM, the selective affinity of PAM for certain substrates may provide a mechanism for the differential amidation of different hormones within a given tissue or cell.
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PMID:Gastrin-amidating enzyme in the porcine pituitary and antrum. Characterization of molecular forms and substrate specificity. 198 4

Formation of biologically active amidated gastrin from glycine-extended progastrin processing intermediates (G-Gly) is achieved via the action of peptidyl-glycyl alpha-amidating monooxygenase. Since this enzyme requires copper for optimal activity, we examined the effects of a known copper chelator, diethyldithiocarbamate (DDC), on gastrin posttranslational processing and gastric acid secretion in vivo. DDC (400 mg.kg-1.day-1 ip X 3 days) administered to male Sprague-Dawley rats decreased antral amidated gastrin content, but increased antral G-Gly content. The ratio of amidated gastrin to G-Gly, which reflects in situ amidating activity, was decreased in DDC-treated rats. In contrast, tissue amidating potential, assayed directly under optimal copper concentrations in vitro, was increased in the antrum and unchanged in the pituitary. DDC markedly increased both basal and gastrin-stimulated gastric acid outputs despite the presence of normal serum amidated gastrin levels. These results suggest that copper chelation with DDC inhibits amidating activity in situ but selectively increases antral amidating enzyme synthesis. The marked increase in acid secretion despite normal circulating amidated gastrin concentrations, combined with the enhanced secretory response to exogenously administered gastrin, suggests the possibility that gastrin receptors are upregulated by the events precipitated via DDC administration.
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PMID:Inhibition of the alpha-amidation of gastrin: effects on gastric acid secretion. 215 43

Pancreatic polypeptide (PP) and gastrin are initially synthesized as larger precursors that require posttranslational processing to produce the biologically active peptides. These steps include tryptic cleavage at paired basic residues, their subsequent removal by carboxypeptidase H, and formation of a carboxy-terminal amide moiety via the action of peptidyl-glycine alpha-amidating monooxygenase (PAM). Although these posttranslational processing reactions are presumed to occur primarily in the secretory granule of endocrine cells, nonendocrine cells that do not possess these structures nevertheless are able to posttranslationally process a wide variety of proteins destined for export. In these studies we sought to determine whether the mechanisms for prohormone processing are present in nonendocrine cell lines. We examined two fibroblast cell lines (psi-2, BHK) a hepatocyte cell line (Hepa), and an exocrine pancreatic cell line (AR42J). We used the pZIPneo(SVX) retroviral vector to express cDNA clones encoding human PP and gastrin in the nonendocrine cells. Transfected psi-2, BHK, and Hepa cells produced a precursor of PP that appeared to be secreted constitutively, with little remaining in intracellular stores. Almost no posttranslational processing of the PP precursor was evident in these cells. By contrast, AR42J cells were capable of expressing and storing fully processed and carboxy-terminally amidated PP and gastrin. These data support the notion that the sorting mechanisms in endocrine and exocrine cells are similar and that the posttranslational processing of peptide hormone precursors requires storage in secretory granules.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Expression and processing of prohormones in nonendocrine cells. 768 30

To confirm the results of a previous report on the use of monoclonal antibodies in immunocytochemical assays of sputums for the early detection of lung cancer, we designed a new prospective trial in an independent clinical trial population. Since well-characterized Stage I resected non-small cell lung cancer patients have a low rate of tumor relapse and a high (1-3%/year) chance of developing a second primary lung cancer, they comprise a very favorable group for conducting an early lung cancer detection trial. The rate of new lung cancer is about 10-fold in excess of a standard "high" risk population of smokers. To optimize the chance for a favorable outcome, all of the technical components for the trial have been systematically evaluated to ensure that optimal procedures are employed. For example, automated immunostaining of the sputum specimens will be performed. Bronchial lavages will be analyzed in a subset of the trial participants to define additional targets for early lung cancer detection. Two markers will be quantitated, including gastrin releasing peptide and peptidyl glycine alpha-amidating monooxygenase activity. These two markers assess the epithelium's capacity to produce growth factors which may be central to the biology of tumor promotion. Since these assays have not been performed in this context before, we attempted to optimize the specimen handling to permit the receipt of the material from a range of collaborating clinical sites in a condition that permits accurate quantitation of these two biomarkers. Efforts to standardize the assay endpoint stimulated the development of computer-assisted methods of immunocytochemical analysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Prospective trial evaluating immunocytochemical-based sputum techniques for early lung cancer detection: assays for promotion factors in the bronchial lavage. 841 89

Monitoring respiratory epithelial biology may reveal individuals with incipient lung cancer. The expression of neuroendocrine (NE) markers in pulmonary epithelium is thought to be central to lung development, repair of injury and may contribute to carcinogenesis. In this study, we evaluate several candidate NE markers to determine the feasibility of prospective analysis of clinical specimens. The potential NE markers include the enzyme L-DOPA decarboxylase (DDC), the neuropeptide gastrin releasing peptide (GRP), and peptidyl-glycine alpha-amidating monooxygenase (PAM), the bifunctional enzyme responsible for the final bioactivation step of many neuropeptides. A comparison of PAM activity and DDC levels in 30 lung cancer cell lines indicated that peptide amidating activity may be an indicator of NE status. Bronchoalveolar lavage (BAL) fluid from subjects at risk of developing second primary lung cancer and from volunteers was obtained. The activity of the first PAM enzyme, peptidylglycine alpha-hydroxylating monooxygenase (PHM), ranged from not detectable to 507 pmol/h/mg protein in 57 specimens. The second PAM enzyme, peptidylamidoglycolate lyase (PAL), ranged from not detectable to 414 pmol/h/mg protein in 56 specimens. Using cluster analysis by the average linkage method, a group of enzyme values with PHM greater than 230 pmol/h/mg protein was determined. Long-term follow-up of these patients for new second primary lung cancers may help to determine the potential predictive value of PAM detected in the BAL fluid.
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PMID:Peptide amidating activity in human bronchoalveolar lavage fluid. 879 7

Gastrin requires extensive posttranslational processing for full biological activity. It is presumed that progastrin is cleaved at pairs of basic amino acids by a prohormone convertase to form a glycine-extended intermediate (G-Gly) that serves as a substrate for peptidyl-glycine alpha-amidating monooxygenase (PAM), resulting in COOH-terminally amidated gastrin. To confirm the nature of progastrin processing in a primary cell line, we performed [(35)S]methionine-labeled pulse-chase biosynthetic experiments in canine antral G cells. Radiolabeled progastrin reached a peak earlier than observed for G-Gly or amidated gastrin. G-Gly radioactivity accumulated in G cells and preceded the appearance of radioactivity in amidated gastrin. The conversion of G-Gly to amidated gastrin was enhanced by the PAM cofactor ascorbic acid. To determine whether one member of the prohormone convertase family (PC2) was responsible for progastrin cleavage, G cells were incubated with PC2 antisense oligonucleotide probes. Cells treated with antisense probes had reduced PC2 expression, an accumulation of radiolabeled progastrin, and a delay in the formation of amidated gastrin. Progastrin in antral G cells is cleaved via PC2 to form G-Gly that is converted to amidated gastrin via the actions of PAM.
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PMID:Gastrin biosynthesis in canine G cells. 1196 Jul 73