共查询到20条相似文献,搜索用时 15 毫秒
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A nucleosidase activity has been isolated from Lactobacillus acidophilus which rapidly hydrolyses N-6 (delta-2-isopentenyl) adenosine to its corresponding base, N-6(delta-2-isopentenyl) adenine. The activity can be distinguished from the spleen exzyme (EC. 2.4.2.1), a purine nucleoside transferase, on the basis of its substrate specificity, electrophoretic behavior, and nondependence on phosphate. The bacterial enzyme hydrolyzes both inosine and isopentenyl adenosine, giving Km values of 63.3muM and 177 muM respectively. The presence of this enzyme in bacteria counts for the rapid conversion of the parent nucleoside to isopentenyl adenine, which has been observed in these cells. The enzyme thus assumes importance as one of the catabolic activities available to the cell for metabolizing the cytokinin, N-6-(delta-2-isopentenyl) adenosine. 相似文献
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D M Logan 《Journal of lipid research》1972,13(1):137-138
The isoprenoid precursors Delta(3)-isopentenyl pyrophosphate and gamma,gamma-dimethylallyl pyrophosphate (Delta(2)-isopentenyl pyrophosphate) have been separated by thin-layer chromatography. The products from Delta(2)-isopentenyl pyrophosphate incubated under various conditions of pH and temperature have been separated, and the survival of Delta(2)-isopentenyl pyrophosphate under these conditions has been calculated. The acid-labile Delta(2)-isopentenyl pyrophosphate can be stored indefinitely at pH 11.5 and -100 degrees C. 相似文献
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Effect of ribosylzeatin isomers on the enzymatic degradation of N6-(delta2-isopentenyl) adenosine. 总被引:1,自引:0,他引:1 下载免费PDF全文
Cytokinin oxidase has been partially purified from cultured tobacco tissue. This enzyme converts N6-(delta2-isopentenyl)-adenosine to adenosine. The reaction is inhibited by the two isomers of ribosylzeatin [n6-4-hydroxy-3-methylbut-2-enyl)adenosine]. Trans-ribosylzeatin inhibits the reaction more than the cis-isomer. 相似文献
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C Jayabaskaran 《Biochemistry international》1984,8(2):257-264
Antibodies specific for N6-(delta 2-isopentenyl) adenosine (i6A) were immobilized on Sepharose and this adsorbent (Sepharose-anti-i6A) was used to selectively isolate bacteriophage T4 tRNA precursors containing i6A/ms2i6A from an unfractionated population of 32P-labeled T4 RNAs. The results showed that antibodies to i6A selectively bound only those tRNA precursors containing i6A/ms2i6A. Binding of tRNA precursors by antibody and specificity of the binding was assessed by membrane binding using 32P-labeled tRNA precursor. Binding was highly specific for i6A/ms2i6A residues in the tRNA precursors. This binding can be used to separate modified from unmodified precursor RNAs and to study the biosynthetic pathways of tRNA precursors. 相似文献
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Molecular cloning of the Escherichia coli miaA gene involved in the formation of delta 2-isopentenyl adenosine in tRNA. 总被引:7,自引:6,他引:1 下载免费PDF全文
Escherichia coli mia strains were shown to lack delta 2-isopentenylpyrophosphate transferase activity, the first step in the synthesis of the 2-methylthio derivative of 6-(delta 2-isopentenyl) adenosine (ms2i6A). A double mutant, rpsL (Smp) miaA, was streptomycin dependent. The wild-type miaA gene was cloned by selecting for lambda recombinant bacteriophage which eliminated the streptomycin-dependent phenotype and was subsequently recloned into plasmid vectors. The cloned miaA gene restored the ms2i6A modification to tRNA. The miaA gene mapped to 95 min on the E. coli map, and we propose the order mutL-miaA-hflA-purA. 相似文献
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Purification of antibodies for the cytokinin N6-(delta 2-isopentenyl) adenosine by affinity chromatography. 下载免费PDF全文
Isopentenyl adenosine antibodies useful in the investigations of the "cytokinin" functions of isopentenyl adenosine were purified by affinity chromatography. Using different affinity columns, the antibodies were purified to near complete purity. Analyses of the purified proteins revealed the presence of isopentenyl adenosine binding proteins in normal rabbit serum, which presence supports a suggested role for isopentenyl adenosine and its related compounds in animal cell division in vivo. 相似文献
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Formation of an antibody with serologic specificity for N 6 -( 2 -isopentenyl) adenosine 总被引:8,自引:0,他引:8
B Hacker H Van Vunakis L Levine 《Journal of immunology (Baltimore, Md. : 1950)》1972,108(6):1726-1728
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Blad CC von Frijtag Drabbe Künzel JK de Vries H Mulder-Krieger T Bar-Yehuda S Fishman P Ijzerman AP 《Purinergic signalling》2011,7(4):453-462
We tested a panel of naturally occurring nucleosides for their affinity towards adenosine receptors. Both N
6-(2-isopentenyl)adenosine (IPA) and racemic zeatin riboside were shown to be selective human adenosine A3 receptor (hA3R) ligands with affinities in the high nanomolar range (K
i values of 159 and 649 nM, respectively). These values were comparable to the observed K
i value of adenosine on hA3R, which was 847 nM in the same radioligand binding assay. IPA also bound with micromolar affinity to the rat A3R. In a functional assay in Chinese hamster ovary cells transfected with hA3R, IPA and zeatin riboside inhibited forskolin-induced cAMP formation at micromolar potencies. The effect of IPA could be
blocked by the A3R antagonist VUF5574. Both IPA and reference A3R agonist 2-chloro-N
6-(3-iodobenzyl)adenosine-5′-N-methylcarboxamide (Cl-IB-MECA) have known antitumor effects. We demonstrated strong and highly similar antiproliferative
effects of IPA and Cl-IB-MECA on human and rat tumor cell lines LNCaP and N1S1. Importantly, the antiproliferative effect
of low concentrations of IPA on LNCaP cells could be fully blocked by the selective A3R antagonist MRS1523. At higher concentrations, IPA appeared to inhibit cell growth by an A3R-independent mechanism, as was previously reported for other A3R agonists. We used HPLC to investigate the presence of endogenous IPA in rat muscle tissue, but we could not detect the compound.
In conclusion, the antiproliferative effects of the naturally occurring nucleoside IPA are at least in part mediated by the
A3R. 相似文献
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