• Reproductive and Developmental Biology
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• v.28 no.4
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• pp.267-273
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• 2004

Maturation of oocytes is maintained by complex procedures along with follicular genesis and is a critical step for embryonic development. Purine known as an oocyte maturation regulator is present in follicular fluid. In this study, the roles of guanosine as a strong inhibitor of GVBD and a modulator of cyclic GMP concentration in ooyctes were revealed. Denuded immature oocytes were treated with guanosine, and the maturation rates and cGMP concentration of oocytes were measured. GVBD was blocked in a concentration dependent manner by guanosine, but this effect was reversible. However, GVBD was lagged yet not significant by adenosine. Both guanosine and adenosine modified cGMP concentration in oocytes. The characteristic of the guanosine-treated oocyte was significantly higher cGMP compared with the adenosine-treated oocyes at initial time of the maturation. Based these results, guanosine may be a strong and reversible GVBD inhibitor. Although the precise mechanism of guanosine presently is unclear, the results suggest that guanosine may lead the accumulation of cGMP in oocyte cytoplasm, which in turn suppresses GVBD.

• Korean Journal of Animal Reproduction
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• v.21 no.2
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• pp.123-130
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• 1997

Normal maturation of the mammalian oocytes is prerequisite for the fertilization and the early embryonic development. We have been tested the effects of purine and its de novo synthetic inhibitor, azaserine(Aza) on the maturation of germinal vesicle(GV) and germinal vesicle breakdown(GVBD) mouse oocytes. Denude-immature oocytes were cultivated in the media containing adenosine, guanosine, and/or azaserine, and checked the matruation stage by monitoring the prominent morphological changes. In GV stage oocytes, GV was arrested temporarily by the adenosine(1.0%) and protractedly by the guanosine(65.9%, P<0.001). The regression was increased significantly at the adenosine(90%, P<0.001) but decreased at the guanosine(1.6%, P<0.05). Inhibiting the de novo synthesis of purine, nuclear maturation rate was increase(90.4% : 96.7%), but GV arrest was significantly increased by cotreatment with guanosine(P<0.001). Polar body extraction significantly was increased at the Aza(P<0.05), but not in others. In GVBD oocytes, adenosine itself did not affect GVBD arrest. Guanosine, on the other hand, elevated GVBD arrest rate(P<0.001), but co-treated with Aza, decreased GVBD arrest(P<0.001). Aza increased GVBD arrest rate(20.2%, P<0.05) compared with control. From those results, we know that guanosine shows more prominent effect on the inhibition of nuclear maturation at the GV stage, and of the 1st polar body extrusion at the GVBD stage. Adenosine showed the cytoplasmic toxicity at GV stage oocyte. Our data speculate that cytoplasmic cAMP level is auto-regulated by endogenous adenylate cyclase while GVBD is inhibited by guanosine, since purine toxicity is not observed in the GVBD stage. And it is showed that purine metabolism is concerned with nuclear maturation, that the amounts of purine metabolism is not even during the oocyte maturation.

• Archives of Pharmacal Research
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• v.11 no.2
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• pp.155-158
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• 1988

To study the behavior of nucleic acid base in a nonpolar organic solvent, chloreform, we synthesized a derivative of guanosine. This erivative, guanosine-2', 3', 5'- trisobutyrate was obtained by reaction of guanosine with isobutyric anhydride, and identified by TLC, EA, IR and NMR. Hydrogen bonding specificity of this compound was revealed by IR and NMR. The molecules of guanosine 2',3',5'-trisobutyrate are self-associated in nonpolar solvent, and hydrogen bonds by imino protent become important as the concentration increases. In the presence of a cytosine derivative, the self-association of theguanosine drivative is destroyed, resulting from interaction with cytosine derivative.

• Korean Journal of Microbiology
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• v.23 no.3
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• pp.167-171
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• 1985

In order to investigate the origin of the ribityl froup of riboflavin and the involvement of GTP cyclohydrolase II in the riboflavin pathway, we studied the incorporation of $^{14}C-labeled$ guanosine using a well known riboflavin over producer, Ashbya gossypii.Cells were grown in a media containing $(U- ^{14}C)$ guanosine and the riboflavin and GMP were isolated and purifired by column chromatography. The isolated compounds, riboflavin and GMP were labeled in the ribityl and ribosyl side chain and the isoalloxazine and guannine moiety. By comparing the specific radioactivity of each compound we reached a conclusion that the ribose of guanosine is converted directly to the rivityl moiety of riboflavin. The results indicate that biosynthesis of the vitamin begins at the level of a guanosine compound and also suppory the involvement of GTP cyclohydrolase II in one of the early steps in the biosynthetic pathway.

• Korean Journal of Microbiology
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• v.31 no.2
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• pp.148-156
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• 1993

Kinetic parameters of purine nucleoside phosphorylase (PNP) from Saccharomyces cerevisiae were measured. The Michaelis constants determined for substrates of the enzyme were $ 2.0 * 10^{-4}$ M for inosine, $2.0 *10^{-3}$ M for deoxyinosine, $ 2.0 * 10^{-5}$ M for guanosine and $2.0 10 ^{-5}$ M for deoxyguanosine. According to the ratio of relative $K_{cat}$Km, substrate specificity of each nucleoside was in the order of guanosine or deoxyguanosine, inosine and deoxyinosine. Cosubstrate, phosphate, revealed downward curvature in Lineweaver-Burk plot at high concentrations, indicating a negative cooperativity between subunits. The inhibition constants for purine analogs were measured to be $ 6 * 10^{-4}$ M for formycin B as the competitive inhibitor of inosine, $ 9 * 10^{-6}$ M for guanine as the competitive inhibitor of guanosine, $2 * 10^{-4}$ M for hypoxanthine as the non competitive inhibitor of guanosine and $4.5 * 10 ^{-4}$ M for 6-mercaptopurine as the non competitive inhibitor of guanosine. Alternative substrates, guanosine, deoxyguanosine and adenosine were found to act as competitive inhibitors with Ki values o $f^ 2.0 * 10 {-5}$ M, $2.6 * 10^{-5}$ M and $8.5 * 10 ^{-4}$ M, respectively, when inosine was the variable substrate. Guanosine and deoxyguanosine were also observed as competitive inhibitors with the Ki values of $1.8 * 10^{-5}$ M and $ 3.0 * 10^{-5}$ M, respectively, when deoxyinesine was the variable substrate. The results of alternative substrate sstudies suggested that a single enzyme acted on different nucleosides, inosine, deoxyinosine, adenosine, guanosine and deoxyguanosine.e.

• Macromolecular Research
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• v.14 no.4
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• pp.443-448
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• 2006

A novel ${\beta}$-cyclodextrin derivative (CCD-C) was synthesized with chitosan and carboxymethyl-${\beta}$-cyclodextrin. Its structure was characterized by elemental analysis, infrared spectra analysis, and X-ray diffraction analysis. The adsorption properties for guanosine 5'-monophosphate, cytidine 5'-monophosphate and uridine 5'-monophosphate were studied. Experimental results demonstrated that CCD-C had higher adsorption capability for guanosine 5'-monophosphate, and that the adsorption capacity for guanosine 5'-monophosphate was 74.20mg/g. The adsorption capacity was greatly influenced by pH, time and temperature. The introduction of chitosan enhanced the adsorption ability and adsorption selectivity of ${\beta}$-cyclodextrin for guanosine 5'-monophosphate. This novel derivative of chitosan is expected to have wide applications in the separation, concentration and analysis of nucleotides in biological samples.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2005.06a
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• pp.233-244
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• 2005

Guanosine fermentation process can be well predicted and analyzed by the proposed state equations describing the dynamic change of a bioreactor. Pyruvate and alanine were found to be characteristically accumulated along with the decline of the guanosine formation rate during the mid-late phase of the process. The enzymological study of the main pathways in glucose catabolism and the quantitative stoichiometric calculation of metabolic flux distribution revealed that it was entirely attributed to the shift of metabolic flux from hexose monophosphate (HMP) pathway to glycolysis pathway. The process optimization by focusing on the restore of the shift of metabolic flux was conducted and the overcoming the decrease of oxygen uptake rate (OUR) was taken as the relevant factor of the trans-scale operation. As a result, the production of guanosinewas increased from 17 g/L to over 34 g/I.

• Microbiology and Biotechnology Letters
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• v.44 no.1
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• pp.55-61
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• 2016

Sepiapterin, a precursor for tetrahydrobiopterin, is produced in higher mammals using guanosine triphosphate (GTP) as a biosynthetic intermediate. Four genes involved in GTP biosynthesis, namely those of guanosine monophosphate kinase (gmk), nucleoside diphosphate kinase (ndk), guanosine phosphate synthetase (guaA), and inosine-5'-monophosphate dehydrogenase (guaB), were expressed in sepiapterin-producing recombinant Escherichia coli BL21(DE3) to increase intracellular GTP concentration and to improve sepiapterin production concomitantly. Coexpression of gmk, ndk, guaA, and guaB, doubled the intracellular GTP concentration and increased the maximum sepiapterin concentration up to $126.1{\pm}19.3mg/l$ (an increase of 43% compared with control cells) in batch-cultivated recombinant E. coli.

• Environmental Mutagens and Carcinogens
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• v.22 no.2
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• pp.106-111
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• 2002

AG6O, the complex of acriflavine and guanosine, has been shown to possess the synergistic antitumorigenic activity in the previous paper (J. Pharm. Pharmacol. 1997, 49:216). In this study, we have investigated the genotoxic properties of AG60 using in vitro and in vivo system such as Ames bacterial reversion test, chromosomal aberration assay and micronucleus assay. In Ames reverse mutation test, AG60 treatment at the dose range up to 250 $\mu\textrm{g}$/plate caused the dose-independent random induction of the mutagenic colony formation in S. typhimurium TA98, TA100, TA1537, and E. coli WP2uvrA, while any mutagenic effect of AG60 wasn't observed in S. typhimurium TA1535. Any significant chromosomal aberration wasn't observed in chinese hamster lung (CHL) fibroblast cells incubated with PBS or AG60 at the concentrations of 2.5, 5, 10 $\mu\textrm{g}$/$m\ell$ for 24 hours without but even with 59 metabolic activation system for 6 hours. In vivo ICR mice, the intramuscular injection of AG60 at the doses of 7.15, 14.3, and 28.6 mg/kg did not induce the frequency of micronucleus formation. However, mitomycin C, as one of the positive controls at the dose of 2 mg/kg caused the 8.4% induction in the frequency of micronucleus and 24% increase in the chromosomal aberration.

• Archives of Pharmacal Research
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• v.22 no.6
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• pp.619-623
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• 1999

$2^{l},3^{l}$-dideoxyisoguanosine was synthesized from guanosine via intermediate 6-[(4-methyl-phenyl)thio]-2-oxo-9-($2^{l},3^{l},5^{l}$-tri-O-acetyl-$\beta$-D-ribofuranosyl)-2,3-dihydropurine (4). The 2-oxo, 6-amino and $5^{l}$-hydroxy triprotected isoguanosine derivative was utilized to reduce high polarity and promote poor solubility of intermediates. The protecting groups for oxo and 6-amino were easily removed in reduction of olefin in ribose without additional reaction steps.$2^{l},3^{l}$-Vicinal diol in ribose sugar moiety was transformed to olefin with Bu3SnH by radical reaction via bisxanthate. Removing $5^{l}$-O-TBDMS protecting group gave final product, $2^{l},3^{l}$-dideoxyisoguanosine (12) in a 10% overall yield.