Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The genes coding for histidine decarboxylase from a wild-type strain and an autoactivation mutant strain of Lactobacillus 30a have been cloned and expressed in Escherichia coli. The mutant protein, G58D, has a single Asp for Gly substitution at position 58. The cloned genes were placed under control of the beta-galactosidase promoter and the products are natural length, not fusion proteins. The enzyme kinetics of the proteins isolated from E. coli are comparable to those isolated from Lactobacillus 30a. At pH 4.8 the Km of wild-type enzyme is 0.4 mM and the kcat = 2800 min-1; the corresponding values for G58D are 0.5 mM and 2750 min-1. The wild-type and G58D have autoactivation half-times of 21 and 9 h respectively under pseudophysiological conditions of 150 mM K+ and pH 7.0. At pH 7.6 and 0.8 M K+ the half-times are 4.9 and 2.9 h. The relatively slow rate of autoactivation for purified protein and the differences in cellular and non-cellular activation rates, coupled with the fact that wild-type protein is readily activated in wild-type Lactobacillus 30a but poorly activated in E. coli, suggest that wild-type Lactobacillus 30a contains a factor, possibly an enzyme, that enhances the activation rate.
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PMID:Expression and characterization of Lactobacillus 30a histidine decarboxylase in Escherichia coli. 333 96

Histamine production in bacteria-contaminated fish is the result of the presence of bacterial histidine decarboxylase activity, which converts histidine present in muscle proteins to histamine. The fish pathogen Vibrio anguillarum harbors a plasmid-encoded histidine decarboxylase gene (angH) that is essential for biosynthesis of the siderophore anguibactin. However, the role of angH in histamine biosynthesis by this pathogen has not been fully determined. Thus, the objectives of this study were to monitor the production and release of histamine by the wild-type as well as by a plasmidless strain and angH isogenic mutants generated by allelic exchange. Reverse transcription polymerase chain reaction showed that only the wild-type strain expressed angH, while no angH message was detected in the mutants and the plasmidless derivative. The iron uptake-deficient phenotype of one of the angH mutants confirmed the location of the mutation and the unique role of this gene in iron acquisition. Thin-layer chromatography, gas chromatography, and mass spectrometry showed that histamine was released by the strain harboring a wild-type angH gene when grown in excess histidine. This biogenic amine was not detected in the culture supernatants of the plasmidless derivative and the angH mutant when cultured under the same experimental conditions. These results indicate that angH is essential for histamine biosynthesis in V. anguillarum, a compound responsible for food poisoning and potentially involved in bacterial virulence. Thin-layer chromatography of wild-type culture supernatants and beta-galactosidase assays using the isogenic angH mutant demonstrated that the expression of this gene is independent of the histidine concentration of the medium under both iron-rich and iron-limiting conditions.
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PMID:Plasmid-mediated histamine biosynthesis in the bacterial fish pathogen Vibrio anguillarum. 957 Nov 39

Somatostatin is found in neurons and endocrine cells in the gastrointestinal tract. The actions of somatostatin are mediated by a family of G-protein-coupled receptors that compose five subtypes (SSTR1-5), each of which is encoded by a separate gene. lacZ "knockin" mice, in which the reporter gene lacZ was engineered into the genomic locus of Sstr2 by gene targeting, were used to examine the expression pattern of Sstr2 and identify potential targets for neurally released and hormonal somatostatin in the gastrointestinal tract. In the body of the stomach, a large proportion of epithelial cells and subpopulations of myenteric neurons expressed Sstr2. Double- or triple-labeling with antisera to H(+)K(+)ATPase (to identify parietal cells) and/or histidine decarboxylase (to identify enterochromaffin-like [ECL] cells) combined with beta-galactosidase staining revealed that both parietal cells and ECL cells expressed Sstr2, and these two cell types accounted for almost all of the Sstr2-expressing epithelial cells. Somatostatin inhibits gastric acid secretion. The presence of SSTR2 on both parietal and ECL cells suggests that somatostatin acting on SSTR2 may reduce acid secretion by both acting directly on parietal cells and by reducing histamine release from ECL cells. In the small and large intestine, subpopulations of neurons in the myenteric and submucosal plexuses expressed Sstr2, and many of the Sstr2-expressing myenteric neurons also showed SSTR2(a) immunostaining. Most of Sstr2-expressing neurons in the myenteric plexus showed nitric oxide synthase (NOS) immunoreactivity. Previous studies have shown that NOS neurons are descending interneurons and anally projecting, inhibitory motor neurons. Thus, somatostatin acting at SSTR2 receptors on NOS neurons might modulate descending relaxation.
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PMID:Identification of cells expressing somatostatin receptor 2 in the gastrointestinal tract of Sstr2 knockout/lacZ knockin mice. 1244 23