Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Asparagine, the primary assimilation product from N2 fixation in temperate legumes and the predominant nitrogen transport product in many plant species, is synthesized via asparagine synthetase (AS; EC 6.3.5.4). Here, we report the isolation and characterization of a cDNA and a gene encoding the nodule-enhanced form of AS from alfalfa. The AS gene is comprised of 13 exons separated by 12 introns. The 5' flanking region of the AS gene confers nodule-enhanced reporter gene activity in transformed alfalfa. This region also confers enhanced reporter gene activity in dark-treated leaves. These results indicate that the 5' upstream region of the AS gene contains elements that affect expression in root nodules and leaves. Both AS mRNA and enzyme activity increased approximately 10- to 20-fold during the development of effective nodules. Ineffective nodules have strikingly reduced amounts of AS transcript. Alfalfa leaves have quite low levels of AS mRNA and protein; however, exposure to darkness resulted in a considerable increase in both. In situ hybridization with effective nodules and beta-glucuronidase staining of nodules from transgenic plants showed that AS is expressed in both infected and uninfected cells of the nodule symbiotic zone and in the nodule parenchyma. RNA gel blot analysis and in situ hybridization results are consistent with the hypothesis that initial AS expression in nodules is independent of nitrogenase activity.
 ...
PMID:Nitrogen assimilation in alfalfa: isolation and characterization of an asparagine synthetase gene showing enhanced expression in root nodules and dark-adapted leaves. 928 11

The production and storage of explosives has resulted in the environmental accumulation of the mutagen 2,4,6-trinitrotoluene (TNT). In order to characterize the production of mutagenic urinary metabolites, 6-week old male Fischer 344 rats were administered 75 mg of TNT/kg or DMSO vehicle by gavage. The animals were placed into metabolism cages, and urine was collected for 24 hr. Following filtration, metabolites in the urine were deconjugated with sulfatase and beta-glucuronidase and concentrated by solid phase extraction. The eluate was fractionated by reverse-phase high-performance liquid chromatography (HPLC) using acetonitrile/water, and the fractions, were solvent exchanged in DMSO by nitrogen evaporation. Each HPLC fraction was bioassayed in strains TA98, TA98NR, TA100, and TA100NR without metabolic activation using a microsuspension modification of the Salmonella histidine reversion assay. Fractions 3, 5-18, 21, 22, and 24-26 contained mutagens detected by strain TA98. In the nitroreductase-deficient strain TA98NR, some mutagenic activity was lost; however, fractions 3, 6, 9-11, 15, and 25 clearly contained direct-acting mutagens. Fewer fractions were positive in strain TA100 (9-16, 19, 20, and 25) with less activity observed in the nitroreductase deficient strain TA100NR (fractions 3, 12, 14, 15, and 25). Although some mutagenic activity coeluted with known TNT metabolite standards, there were still many unidentified mutagenic peaks.
 ...
PMID:Mutagenicity of HPLC-fractionated urinary metabolites from 2,4,6-trinitrotoluene-treated Fischer 344 rats. 936 8

Although the control of carbon fixation and nitrogen assimilation has been studied in detail, relatively little is known about the regulation of carbon and nitrogen flow into amino acids. In this paper we report our study of the metabolic regulation of expression of an Arabidopsis aspartate kinase/homoserine dehydrogenase (AK/HSD) gene, which encodes two linked key enzymes in the biosynthetic pathway of aspartate family amino acids. Northern blot analyses, as well as expression of chimeric AK/HSD-beta-glucuronidase constructs, have shown that the expression of this gene is regulated by the photosynthesis-related metabolites sucrose and phosphate but not by nitrogenous compounds. In addition, analysis of AK/HSD promoter deletions suggested that a CTTGACTCTA sequence, resembling the binding site for the yeast GCN4 transcription factor, is likely to play a functional role in the expression of this gene. Nevertheless, longer promoter fragments, lacking the GCN4-like element, were still able to confer sugar inducibility, implying that the metabolic regulation of this gene is apparently obtained by multiple and redundant promoter sequences. The present and previous studies suggest that the conversion of aspartate into either the storage amino acid asparagine or aspartate family amino acids is subject to a coordinated, reciprocal metabolic control, and this biochemical branch point is a part of a larger, coordinated regulatory mechanism of nitrogen and carbon storage and utilization.
 ...
PMID:Expression of an arabidopsis aspartate Kinase/Homoserine dehydrogenase gene is metabolically regulated by photosynthesis-related signals but not by nitrogenous compounds 950 Nov 34

NADH-dependent glutamate synthase (NADH-GOGAT; EC 1.4.1.14) is a key enzyme in primary nitrogen assimilation in alfalfa (Medicago sativa L.) root nodules. Here we report that in alfalfa, a single gene, probably with multiple alleles, encodes for NADH-GOGAT. In situ hybridizations were performed to assess the location of NADH-GOGAT transcript in alfalfa root nodules. In wild-type cv Saranac nodules the NADH-GOGAT gene is predominantly expressed in infected cells. Nodules devoid of bacteroids (empty) induced by Sinorhizobium meliloti 7154 had no NADH-GOGAT transcript detectable by in situ hybridization, suggesting that the presence of the bacteroid may be important for NADH-GOGAT expression. The pattern of expression of NADH-GOGAT shifted during root nodule development. Until d 9 after planting, all infected cells appeared to express NADH-GOGAT. By d 19, a gradient of expression from high in the early symbiotic zone to low in the late symbiotic zone was observed. In 33-d-old nodules expression was seen in only a few cell layers in the early symbiotic zone. This pattern of expression was also observed for the nifH transcript but not for leghemoglobin. The promoter of NADH-GOGAT was evaluated in transgenic alfalfa plants carrying chimeric beta-glucuronidase promoter fusions. The results suggest that there are at least four regulatory elements. The region responsible for expression in the infected cell zone contains an 88-bp direct repeat.
 ...
PMID:NADH-glutamate synthase in alfalfa root nodules. Genetic regulation and cellular expression. 1006 21

A cDNA clone encoding alanine aminotransferase (AlaAT) has isolated from randomly sequenced clones derived from a cDNA library of maturing rice seeds by comparison to previously identified genes. The deduced amino acid sequence was 88% and 91% homologous to those of the enzymes from barley and broomcorn millet (Panicum miliaceum), respectively. Using this cDNA as a probe, we isolated and sequenced the corresponding genomic clone. Comparison of the sequences of the cDNA and the genomic gene revealed that the coding region of the gene was interrupted by 14 introns 66 to 1547 bp long. Northern and western blotting analyses showed that the gene was expressed at high levels in developing seeds. When the 5'-flanking region between -930 and +85 from the site of initiation of transcription was fused to a reporter gene for beta-glucuronidase (GUS) and then introduced into the rice genome, histochemical staining revealed strong GUS activity in the inner endosperm tissue of developing seeds and weak activity in root tips. Similar tissue-specific expression was also detected by in situ hybridization. These results suggest that AlaAT is involved in nitrogen metabolism during the maturation of rice seed.
 ...
PMID:Molecular characterization of a gene for alanine aminotransferase from rice (Oryza sativa). 1008 Jul 17

In bacteria and yeast, glutamine synthetase (GS) expression is tightly regulated by the metabolic status of the cell, both at the transcriptional and posttranscriptional levels. We discuss the relative contributions of light and metabolic cues on the regulation of members of the GS gene family (chloroplastic GS2 and cytosolic GS1) in Arabidopsis. These studies reveal that the dramatic induction of mRNA for chloroplastic GS2 by light is mediated in part by phytochrome and in part by light-induced changes in sucrose (Suc) levels. In contrast, the modest induction of mRNA for cytosolic GS1 by light is primarily mediated by changes in the levels of carbon metabolites. Suc induction of mRNA for GS2 and GS1 occurs in a time- and dose-dependent manner. Suc-induced changes in GS mRNA levels were also observed at the level of GS enzyme activity. In contrast, amino acids were shown to antagonize the Suc induction of GS, both at the level of mRNA accumulation and that of enzyme activity. For GS2, the gene whose expression was the most dramatically regulated by metabolites, we used a GS2 promoter-beta-glucuronidase fusion to demonstrate that transcriptional control is involved in this metabolic regulation. Our results suggest that the metabolic regulation of GS expression in plants is controlled by the relative abundance of carbon skeletons versus amino acids. This would allow nitrogen assimilation into glutamine to proceed (or not) according to the metabolic status and biosynthetic needs of the plant. This type of GS gene regulation is reminiscent of the nitrogen regulatory system in bacteria, and suggests an evolutionary link between metabolic sensing and signaling in bacteria and plants.
 ...
PMID:Carbon and amino acids reciprocally modulate the expression of glutamine synthetase in Arabidopsis. 1048 86

In many plants, cysteine proteinases play essential roles in a variety of developmental and physiological processes. In rice (Oryza sativa), REP-1 is a primary cysteine proteinase responsible for the digestion of seed storage proteins to provide nutrients to support the growth of young seedlings. In the present study, the gene encoding REP-1 was isolated, characterized, and designated as OsEP3A. An OsEP3A-specific DNA probe was used to study the effect of various factors on the expression of OsEP3A in germinating seeds and vegetative tissues of rice. The expression of OsEP3A is hormonally regulated in germinating seeds, spatially and temporally regulated in vegetative tissues, and nitrogen-regulated in suspension-cultured cells. The OsEP3A promoter was linked to the coding sequence of the reporter gene, gusA, which encodes beta-glucuronidase (GUS), and the chimeric gene was introduced into the rice genome. The OsEP3A promoter is sufficient to confer nitrogen regulation of GUS expression in suspension-cultured cells. Histochemical studies also indicate that the OsEP3A promoter is sufficient to confer the hormonal regulation of GUS expression in germinating seeds. These studies demonstrate that in rice the REP-1 protease encoded by OsEP3A may play a role in various physiological responses and processes, and that multiple mechanisms regulate the expression of OsEP3A.
 ...
PMID:Multiple mode regulation of a cysteine proteinase gene expression in rice. 1063 Dec 49

Recently, the detection of urinary glucuronide conjugates of nicotine and its two major metabolites, trans-3'-hydroxycotinine and cotinine, showed that glucuronidation is an important pathway of nicotine metabolism in humans. (S)-(-)-Nicotine-N(+)-1-beta-glucuronide (quaternary N-glucuronide with linkage through the pyridino-nitrogen of nicotine) was shown to be an important nicotine metabolite of humans in vivo. The present study was undertaken to develop an animal model for this process, in order to ascertain the factors influencing quaternary N-glucuronide formation. (S)-(-)-Nicotine-N(+)-1-beta-glucuronide was formed in vitro when [2'-14C]-nicotine was incubated with Triton X-100 activated marmoset hepatic microsomes in the presence of uridine diphosphoglucuronic acid; it was not formed when activated microsomal preparations of rabbit, guinea-pig, or rat were used as enzyme source. The glucuronide was characterised by comparison with authentic synthetic (S)-(-)-nicotine-N(+)-1-beta-glucuronide using HPLC. The rate of formation of the glucuronide was almost linear during up to four hours of incubation, but still only accounted for a maximum of 6.0% of the available substrate at the end of five hours incubation. The synthetic and biosynthetic (S)-(-)-nicotine-N(+)-1-beta-glucuronides were hydrolysed by beta-glucuronidase and alkali, but were resistant to acid hydrolysis. The results support the concept that the marmoset may be a good animal species to mimic man in studies of nicotine metabolism during exposure to tobacco smoke. In vitro studies using (+/-)-trans-3'-hydroxycotinine or (S)-(-)-cotinine (as potential substrate) and [14C]-uridine diphospho-glucuronic acid (as cofactor) failed to produce any new radiolabelled glucuronide when the above microsomal preparations were used.
 ...
PMID:Evidence for the biosynthesis of A glucuronide conjugate of (S)-(-)-nicotine, but not (S)-(-)-cotinine or (+/-)-trans-3'-hydroxycotinine by marmoset hepatic microsomes. 1071 38

A promoter tagging program in the legume Lotus japonicus was initiated to identify plant genes involved in the nitrogen-fixing symbiosis between legumes and rhizobia. Seven transformed plant lines expressing the promoterless reporter gene uidA (beta-glucuronidase; GUS) specifically in roots and/or nodules were identified. Four of these expressed GUS in the roots only after inoculation with nodule-forming Mesorhizobium loti. In one line (T90), GUS activity was found in the root epidermis, including root hairs. During seedling growth, GUS expression gradually became focused in developing nodules and disappeared from root tissue. No GUS activity was detected when a non-nodulating mutant of M. loti was used to inoculate the plants. The T-DNA insertion in this plant line was located 1.3 kb upstream of a putative coding sequence with strong homology to calcium-binding proteins. Four motifs were identified, which were very similar to the "EF hands" in calmodulin-related proteins, each binding one Ca2+. We have named the gene LjCbp1 (calcium-binding protein). Northern (RNA) analyses showed that this gene is expressed specifically in roots of L. japonicus. Expression was reduced in roots inoculated with non-nodulating M. loti mutants and in progeny homozygous for the T-DNA insertion, suggesting a link between the T-DNA insertion and this gene.
 ...
PMID:Mesorhizobium loti increases root-specific expression of a calcium-binding protein homologue identified by promoter tagging in Lotus japonicus. 1083 Feb 60

Three types of callus tissues established from anther culture of eleven doubled haploid (DH) lines of wheat (Triticum aestivum L.) were evaluated for their ability in enhancing friable embryogenic (Type II) culture differentiation and genetic transformation. Differences between types of callus inocula were highly significant (P < 0.001), suggesting that the quality of the initial callus explant is of profound importance in encouraging the proliferation of Type II cultures. Other factors found to be crucial included weekly subculture of friable embryogenic callus tissues on a maintenance medium containing 30 microM dicamba and a predominance of amino-acid nitrogen supplement. Transfer and integration of the beta-glucuronidase gene was also affected by the type of inoculum when suitable embryogenic cell cultures were transformed using silicon carbide whiskers and high velocity microprojectiles. Expression of the hygromycin phosphotransferase selectable marker gene sequence was confirmed in all the stably transformed cell lines maintained on selection media containing lethal levels of hygromycin. Comparatively, there were differences in the frequency of regenerable, transgenic clonal segments between whisker-treated and microprojectile bombarded tissues mainly as a result of the fact that cultures vortexed with whiskers were more capable of post-treatment cell proliferation and embryo differentiation than those bombarded with cDNA-coated microprojectiles. Conditions for obtaining these results are outlined and discussed in relation to the suitability of the two transformation strategies for producing transgenic cell aggregates of wheat.
 ...
PMID:Cytodifferentiation and transformation of embryogenic callus lines derived from anther culture of wheat. 1093 25


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>