• The Korean Journal of Physiology and Pharmacology
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• v.14 no.3
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• pp.145-150
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• 2010

Adenosine (Ado) is an important mediator of the endogenous defense against ischemia-induced injury in the heart. The action of Ado is mediated by activation of G protein-gated inwardly rectifying $K^+$ (GIRK) channels. In turn, GIRK channels are inhibited by reducing phosphatidylinositol 4,5-bisphosphate ($PIP_2$) through Gq protein-coupled receptors (GqPCRs). We previously found that GIRK channels activated by acetylcholine, a muscarinic M2 acetylcholine receptor agonist, are inhibited by GqPCRs in a receptor-specific manner. However, it is not known whether GIRK channels activated by Ado signaling are also regulated by GqPCRs. Presently, this was investigated in mouse atrial myocytes using the patch clamp technique. GIRK channels were activated by $100\;{\mu}M$ Ado. When Ado was repetitively applied at intervals of 5~6 min, the amplitude of second Ado-activated GIRK currents ($I_{K(Ado)}$) was $88.3{\pm}3.7%$ of the first $I_{K(Ado)}$ in the control. Pretreatment of atrial myocytes with phenylephrine, endothelin-1, or bradykinin prior to a second application of Ado reduced the amplitude of the second $I_{K(Ado)}$ to $25.5{\pm}11.6%$, $30.5{\pm}5.6%$, and $96.0{\pm}2.7%$, respectively. The potency of $I_{K(Ado)}$ inhibition by GqPCRs was different with that observed in acetylcholine-activated GIRK currents ($I_{K(ACh)}$) (endothelin-1>phenylephrine>bradykinin). $I_{K(Ado)}$ was almost completely inhibited by $500\;{\mu}M$ of the $PIP_2$ scavenger neomycin, suggesting low $PIP_2$ affinity of $I_{K(Ado)}$. Taken together, these results suggest that the crosstalk between GqPCRs and the Ado-induced signaling pathway is receptor-specific. The differential change in $PIP_2$ affinity of GIRK channels activated by Ado and ACh may underlie, at least in part, their differential responses to GqPCR agonists.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.171-174
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• 2005

• YAKHAK HOEJI
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• v.38 no.4
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• pp.430-439
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• 1994

S-Adenosyl-L-methionine synthetase (ATP: methionine S-Adenosyltransferase, EC 2.5.1.6; AdoMet synthetase) catalyzes the biosynthesis of S-Adenosyl-L-methionine(AdoMet) from methionine in the presence of ATP. To elucidate the role of transmethylation reaction in the pancreatic tissues, we examined AdoMet synthetase and isozyme activities, and AdoMet contents in the various tissues. The activities of AdoMet synthetase marked the highest in the kidney, and the lowest in the testis among the various tissues of rat. Considerable amounts of AdoMet synthetase activities were detected in the pancreatic tissues of various animals except for those of frog. The level of ${\alpha}$ and ${\gamma}$ isozyme activities were present in the pancreatic tissues of various animals, while ${\beta}$ isozyme activities were detected as trace. AdoMet synthetase activities of rat brain, liver, testis were decreased with growth. In the rat pancreatic tissues, AdoMet synthetase activities were increased during 16 days after birth and then decreased between 16 and 47 days of age. Levels of AdoMet contents of rat brain and testis were decreased with growth. However, AdoMet contents of rat pancreas were decreased until 26 days of age, and then increased thereafter. AdoMet synthetase isozyme patterns did not vary with growth in the pancreas and testis. But, in the liver, ${\beta}$ form is strikingly increased with growth.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.235.3-236
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• 2003

S-adenosyl-L-homocysteine(AdoHcy) is the product of all biological methylation in which S-adenosyl-L-methionine (AdoMet) is utilized as a methyl donor and is reversibly hydrolyzed to L-homocysteine and adenosine by AdoHcy hydrolase physiologically. Inhibition of this enzyme results in intracelluar accumulation of AdoHcy leading to a feedback inhibition of AdoMet-dependent methylation reactions which are essential for viral replication. (omitted)

• BMB Reports
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• v.39 no.6
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• pp.730-736
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• 2006

To evaluated the effect of recombinant adenovirus Ad-ODC-AdoMetDCas which can simultaneously express both antisense ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) on cell cycle distribution in colorectal cancer cell and investigated underlying regulatory responses, human colorectal cancer cells HT-29 were cultured in RPMI 1640 medium and infected with Ad-ODC-AdoMetDCas. Cell cycle progression was detected by flow cytometry analysis. The expression levels of cell cycle regulated proteins were measured by Western blot analysis. The mRNA level of cyclin D1 was measured by RT-PCR. And a luciferase reporter plasmid of cyclin D1 promoter was constructed to observe the effect of Ad-ODC-AdoMetDCas on cyclin D1 promoter activity. The results showed that recombinant adenovirus Ad-ODC-AdoMetDCas significantly induced $G_1$ arrest, decreased levels of cyclin D1 protein and mRNA and suppressed the promoter activity. Ad-ODC-AdoMetDCas also inhibited nuclear translocation of $\beta$-catenin. In conclusion, downregulation of ODC and AdoMetDC mediated by Ad-ODC-AdoMetDCas transfection induces $G_1$ arrest in HT-29 cells and the arrest was associated with suppression of cyclin D1 expression and inhibition of $\beta$-catenin nuclear translocation. As a new anticancer reagent, the recombinant adenovirus Ad-ODC-AdoMetDCas holds promising hope for the therapy of colorectal cancers.

• BMB Reports
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• v.35 no.2
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• pp.178-185
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• 2002

The Arabidopsis thaliana S-Adenosylmethionine decarboxylase (AdoMetDC) cDNA ($GenBank^{TM}$ U63633) was cloned. Site-specific mutagenesis was performed to introduce mutations at the conserved cysteine $Cys^{50}$, $Cys^{83}$, and $Cys^{230}$, and $lys^{81}$ residues. In accordance with the human AdoMetDC, the C50A and C230A mutagenesis had minimal effect on catalytic activity, which was further supported by DTNB-mediated inactivation and reactivation. However, unlike the human AdoMetDC, the $Cys^{50}$ and $Cys^{230}$ mutants were much more thermally unstable than the wild type and other mutant AdoMetDC, suggesting the structural significance of cysteines. Furthermore, according to a circular dichroism spectrum analysis, the $Cys^{50}$ and $Cys^{230}$ mutants show a higher a-helix content and lower coiled-coil content when compared to that of wild type and the other mutant AdoMetDC. Also, the three-dimensional structure of Arabidopsis thaliana AdoMetDC could further support all of the data presented here. Summarily, we suggest that the $Cys^{50}$ and $Cys^{230}$ residues are structurally important.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.163.1-163.1
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• 2003

The inhibitory activities of various analogues of adenosine (Group I, Group II, Group III, Group IV, Group V) were assayed by using recombinant human placental SAH hydrolase. The activity of the SAH hydrolase was determined by measuring the formation of AdoHcy from Ado and Hcy. AdoHcy was analyzed by HPLC using C18 reverse-phase column. The peak of AdoHcy was monitored at 258 nm. Among the tested compounds, fluoroneplanocin A (LJ-276) was the most potent inhibitor.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.1
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• pp.28-39
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• 2007

The purpose of this study is to evaluate the regenerative capacity of reconstruction in the atrophied posterior maxilla by comparing bone graft procedures and alveolar distraction osteogenesis (ADO) techniques. We performed the autogenous iliac bone graft (AGB group, 5 specimens in 3 patients), and the combination (Mixed group, 3 specimens in 3 patients) of the autogenous and deproteinized bovine bone ($Bio-Oss^{(R)}$, Geistlich Co., Switzerland) as the ratio of 2:1 in the sinus floor elevation procedures. ADO procedures using $TRACK^{(R)}$ (KLS Martin Co., Germany) were also performed to augment vertical alveolar height in atrophied posterior maxilla (ADO group, 5 specimens in 4 patients). Newly generated bone tissues were obtained with the 2.0mm diameter trephine bur (3i Co., USA) during implant fixture installation after 5-7 months. Routine histolomorphological observation, immunodot blot assay for quantitative evaluation, and immunohistochemical staining with antibodies to MMP-1, -9, -10, TIMP-1, -2, and BMP-2, -4 were all carried out. Lamellar bone formation was well shown in all specimens and new bone formations of ADO group increased than those of other procedures. In immunohistochemical staining, the strong expression of BMP-2 was shown in all specimens, and immunodot blot assay showed that bone formation is accompanied by the good induction of factors associated with angiogenesis and appeared more increased amount of osteogenic and angiogenic factors in ADO group. ADO is the most effective technique for new bone formation compared to sinus floor elevation with autogenous or mixed bone graft in the atrophied posterior maxilla. In the quantitative immunodot blot assay, the regenerated bone after ADO showed more increased products of VEGF, BMP-2, PCNA and MMP-1 than those after the other procedures, and these findings were able to be confirmed by immunohistochemical stainings.

• BMB Reports
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• v.33 no.1
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• pp.69-74
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• 2000

The Arabidopsis thaliana S-Adenosylmethionine decarboxylase (AdoMetDC) cDNA ($GenBank^{TM}$ U63633) was cloned, then the AdoMetDC protein was expressed and purified. The purified AdoMetDC was inactivated by salicylaldehyde in a pseudo first- order kinetics. The secondorder rate constant for inactivation was 126 $M^{-1}min^{-1}$ with the slope of n=0.73, suggesting that inactivation is the result of the reaction of one lysine residue in the active site of AdoMetDC. Site-specific mutagenesis was performed on the AdoMetDC to introduce mutations in conserved $lysine^{81}$ residues. These were chosen by examination of the conserved sequence and proved to be involved in enzymatic activity by chemical modification. Changing $Lys^{81}$ to alanine showed an altered optimal pH. The substrate also provided protection against inactivation by salicylaldehyde. Considering these results, we suggest that the $lysine^{81}$ residue may be involved in catalytic activity.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.17-17
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• 2003

tRNA (m¹ G37) methyltransferase (TrmD) catalyze s the trans for of a methyl group from S-adenosyl-L-methionine (AdoMet) to G/sup 37/ within a subset of bacterial tRNA species, which have a residue G at 36th position. The modified guanosine is adjacent to and 3' of the anticodon and is essential for the maintenance of the correct reading frame during translation. We have determined the first crystal structure of TrmD from Haemophilus influenzae, as a binary complex with either AdoMet or S-adenosyl-L-homocysteine (AdoHcy), as a ternary complex with AdoHcy/phosphate, and as an apo form. The structure indicates that TrmD functions as a dimer (Figure 1). It also suggests the binding mode of G/sup 36/G/sup 37/ in the active site of TrmD and catalytic mechanism. The N-terminal domain has a trefoil knot, in which AdoMet or AdoHcy is bound in a novel, bent conformation. The C-terminal domain shows a structural similarity to DNA binding domain of trp or tot repressor. We propose a plausible model for the TrmD₂-tRNA₂ complex, which provides insights into recognition of the general tRNA structure by TrmD (Figure 2).