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

S-Adenosylmethionine serves as a methyl group donor in numerous transmethylation reactions and plays a role in the biosynthesis of polyamines and ethylene. We have cloned and sequenced an S-adenosylmethionine synthetase gene (sam-1) of Arabidopsis thaliana. The deduced polypeptide sequence of the enzyme has extensive homology with the corresponding enzymes of Escherichia coli and yeast. Genomic hybridization indicates the presence of two adenosylmethionine synthetase genes per haploid Arabidopsis genome. RNA gel blot analysis shows that adenosylmethionine synthetase mRNA levels are high in stems and roots, correlating well with the higher enzyme activity in stems, compared with leaves. Histochemical analysis of transgenic Arabidopsis plants transformed with a chimeric beta-glucuronidase gene, under the control of 748-base pair 5' sequences of the sam-1 gene, demonstrates that the gene is expressed primarily in vascular tissues. In addition, high expression was observed in sclerenchyma and in the root cortex. A hypothesis for the strong cellular preference in the expression of the sam-1 gene is presented.
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PMID:Strong cellular preference in the expression of a housekeeping gene of Arabidopsis thaliana encoding S-adenosylmethionine synthetase. 253 70

In Arabidopsis the promoter of the gene encoding S-adenosyl-L-methionine synthetase (SAM-S) Psam-1 confers expression preferentially in the vascular tissue. In search for promoters that drive expression in particular cells of the lignifying tissues in trees, we have analyzed the expression pattern conferred by the Psam-1 promoter in transgenic poplar. Histochemical analyses demonstrated beta-glucuronidase (GUS) activity mainly in phloem and cortex tissue throughout the plant, and in root tips. Fluorimetric assays showed high GUS activity in the tissues outside (phloem, cortex and cork) compared to those inside (xylem and pith) of the cambial layer. In contrast, the endogenous SAM-S activity was high in tissues inside and low in tissues outside of the cambial layer. RNA gel blot analysis demonstrated a high transcript level of the endogenous sam-s gene(s) in tissues both outside and inside the cambial layer. This indicates that the low SAM-S activity in the bark was at least partially due to translational and/or post-translational regulation of the endogenous sam-s gene(s). In dormant transgenics, the tissue specificity was conserved, but the activity levels were up to 10-fold reduced.
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PMID:Tissue-specific expression conferred by the S-adenosyl-L-methionine synthetase promoter of Arabidopsis thaliana in transgenic poplar. 903 66

The cDNAs encoding putrescine N-methyltransferase (PMT), which catalyzes the S-adenosylmethionine-dependent N-methylation of putrescine at the first committed step in the biosynthetic pathways of tropane alkaloids, were isolated from Atropa belladonna and Hyoscyamus niger. These PMTs, however, lacked the N-terminal tandem repeat arrays previously found in Nicotiana PMTs. AbPMT1 RNA was much more abundant in the root of A. belladonna than was AbPMT2 RNA. The 5'-flanking region of the AbPMT1 gene was fused to the beta-glucuronidase (GUS) reporter gene and transferred to A. belladonna. Histochemical analysis showed that GUS is expressed specifically in root pericycle cells and that the 0.3-kb 5'-upstream region was sufficient for pericycle-specific expression. Treatment of A. belladonna roots with methyl jasmonate did not up-regulate the expression of GUS or endogenous AbPMT genes. The regulation of tropane alkaloid biosynthesis is discussed and compared with that of nicotine biosynthesis.
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PMID:Expression of Atropa belladonna putrescine N-methyltransferase gene in root pericycle. 1035 17

S-Adenosylmethionine decarboxylase (AdoMetDC) is a key enzyme in polyamine biosynthesis. We show that the plant AdoMetDC activity is subject to post-transcriptional control by polyamines. A highly conserved small upstream open reading frame (uORF) in the AdoMetDC mRNA 5' leader is responsible for translational repression of a downstream beta-glucuronidase reporter cistron in transgenic tobacco plants. Elimination of the small uORF from an AdoMetDC cDNA led to increased relative translational efficiency of the AdoMetDC proenzyme in transgenic plants. The resulting increased activity of AdoMetDC caused disruption to polyamine levels with depletion of putrescine, reduction of spermine levels, and a more than 400-fold increase in the level of decarboxylated S-adenosylmethionine. These changes were associated with severe growth and developmental defects. The high level of decarboxylated S-adenosylmethionine was not associated with any change in 5'-methylcytosine content in genomic DNA and S-adenosylmethionine levels were more or less normal, indicating a highly efficient system for maintenance of S-adenosylmethionine levels in plants. This work demonstrates that uORF-mediated translational control of AdoMetDC is essential for polyamine homeostasis and for normal growth and development.
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PMID:Abrogation of upstream open reading frame-mediated translational control of a plant S-adenosylmethionine decarboxylase results in polyamine disruption and growth perturbations. 1220 86

N-Methyltransferases (NMTs) catalyze the three SAM dependent sequential methylation of xanthosine, producing caffeine in Coffea species. In the present work, a PCR based genome walking method was adopted to isolate and clone the promoter for the NMT gene. Inspection of the promoter sequence revealed the presence of several motifs important for the regulation of the gene expression. The whole fragment was fused to the beta-glucuronidase (gus) reporter gene and used in Agrobacterium tumefaciens mediated transformation of Nicotiana tabacum. GUS assays proved that the isolated promoter was able to direct the expression of the reporter gene in transgenic tobacco. Based on the promoter sequence, primer was designed and the genomic fragment comprising the promoter and its corresponding gene was amplified and cloned. Sequencing of one of the genomic clones revealed the presence of four exons and three introns in NMT gene. The differences in the restriction pattern among the genomic clones were studied using PCR-RFLP. This is the first report of cloning of the promoter for a gene involved in caffeine biosynthetic pathway and it opens up the possibility of studying the molecular mechanisms that regulate the production of caffeine.
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PMID:Isolation of promoter for N-methyltransferase gene associated with caffeine biosynthesis in Coffea canephora. 1604 51