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Research paper thumbnail of Abkhazian crisis: from the Concept of Awareness of Common Threats to the Building of an "Abkhazian Security Community

Grani, 2020

This article is part of a research conducted as part of the Support Program for Doctoral Studies ... more This article is part of a research conducted as part of the Support Program for Doctoral Studies of Shota Rustaveli Georgian National Science Foundation.This article is part of a research conducted as part of the Support Program for Doctoral Studies of Shota Rustaveli Georgian National Science Foundation.Name of the research – "Interdisciplinary analysis of the complex system of the Abkhazian conflict by the method 4D-RAV-17" (grant number – PHDF‐18‐1147). The method is a combination of well-known and innovative approaches and techniques. This article is part of the abovementioned research. The complex system of the Abkhazian conflict in this article received a conditional definition – the Abkhazian crisis. The political component of the complex system is accordingly called the Abkhazian political crisis and is the main object of research in the framework of the article.The article is aimed at solving a specific scientific and applied task – at determining a scientifically...

Research paper thumbnail of Structural and Mutational Analysis of Trypanosoma brucei Prostaglandin H2 Reductase Provides Insight into the Catalytic Mechanism of Aldo-ketoreductases

Journal of Biological Chemistry, 2005

Research paper thumbnail of New anti-malarial phenylpropanoid conjugated iridoids from Morinda morindoides

Bioorganic & Medicinal Chemistry Letters, 2010

Research paper thumbnail of Structure and mutational analysis of Trypanosoma brucei prostaglandin F 2α synthase

Acta Crystallographica Section A Foundations of Crystallography, 2005

Trypanosoma brucei prostaglandin (PG) F 2 synthase (TbPGFS), an aldo-keto reductase, catalyzes th... more Trypanosoma brucei prostaglandin (PG) F 2 synthase (TbPGFS), an aldo-keto reductase, catalyzes the NADPH-dependent reduction of the endoperoxide moiety of PGH 2 to PGF 2. The overproduction of PGF 2 during trypanosomasis causes miscarriage in infected subjects. Here we report the crystal structures of TbPGFS-NADP + bounds citrate or sulfate at 2.1 Å and 2.6 Å resolution respectively. TbPGFS adopts a parallel (/) 8-barrel folds lacking the protrudent loops. The core active site structure is hydrophobic to bind hydrophobic substrates and contains tyrosine, lysine, histidine and aspartate known as a catalytic tetrad which is preserved in most of other aldo-keto reductases. These four residues are said to be indispensable for the reduction of PGH 2 , but mutagenesis shows that Tyr52 and Asp47 are not involved in the enzyme reaction and identifies His110 and Lys77 work as catalytic dyad. His 110 acts as a general acid catalyst, while Lys 77 facilitates proton donation by His 110 through a water molecule and forms a salt-bridge to stabilize the Asp 47 that binds NADPH. By comparing the citrate and sulfate complex structure, we detected that Trp187 holds the nicotinamide ring of NADPH from tilting on the access of PGH 2. These findings reveal a novel catalytic mechanism for the biological reduction of the endoperoxide PGH 2 by an aldo-keto reductase. The structure should allow for rational design of specific inhibitors useful to investigate the physiological roles of TbPGFS in trypanosomes.

Research paper thumbnail of Differentiation and apoptosis in the sleeping sickness inducing parasite Trypanosoma brucei

Eukaryotic parasites still cause fatal diseases (malaria, sleeping sickness, Kala Azar, Chagas di... more Eukaryotic parasites still cause fatal diseases (malaria, sleeping sickness, Kala Azar, Chagas disease etc.) which costs millions of deaths yearly and are hard to control because of insufficient drugs and fast developing resistance mechanisms. We investigate life cycle progression and differentiation processes in Trypanosoma brucei, the causative agent of sleeping sickness. Our results show that this parasite despite of being a protozoan, behaves as a concerted population which communicates by small signalling molecules. Slender parasites are rapidly dividing and thus responsible for the observed increase of parasitemia. They constantly produce a factor of unknown chemical structure, which at a certain cell density reaches a threshold concentration and triggers formation of metabolic and morphological changes within the parasite, thus leading to stumpy form trypanosomes. These are cell cycle arrested and very sensitive against prostaglandin D2, which is also produced by trypanosomes...

Research paper thumbnail of 105(P-46) キノン型ジテルペンの抗トリパノソーマ作用機構(ポスター発表の部)

Research paper thumbnail of Allosteric regulation accompanied by oligomeric state changes of Trypanosoma brucei GMP reductase through cystathionine-β-synthase domain

Nature Communications

Guanosine 5′-monophosphate reductase (GMPR) is involved in the purine salvage pathway and is cons... more Guanosine 5′-monophosphate reductase (GMPR) is involved in the purine salvage pathway and is conserved throughout evolution. Nonetheless, the GMPR of Trypanosoma brucei (TbGMPR) includes a unique structure known as the cystathionine-β-synthase (CBS) domain, though the role of this domain is not fully understood. Here, we show that guanine and adenine nucleotides exert positive and negative effects, respectively, on TbGMPR activity by binding allosterically to the CBS domain. The present structural analyses revealed that TbGMPR forms an octamer that shows a transition between relaxed and twisted conformations in the absence and presence of guanine nucleotides, respectively, whereas the TbGMPR octamer dissociates into two tetramers when ATP is available instead of guanine nucleotides. These findings demonstrate that the CBS domain plays a key role in the allosteric regulation of TbGMPR by facilitating the transition of its oligomeric state depending on ligand nucleotide availability.

Research paper thumbnail of Aeromonas caviae ME-1 xylanases : biochemical studies, biotechnological utilization and analysis of xylanase(s) gene

Research paper thumbnail of Evidence of Prostaglandin Production by the Human Malaria Parasite, Plasmodium Falciparum

South African Journal of Science, 1998

Research paper thumbnail of Purification and Characterization of Aeromonas caviae ME-1 Xylanase V, Which Produces Exclusively Xylobiose from Xylan

A xylanase, which produces exclusively xylobiose from oat spelt and birch xylans, was isolated fr... more A xylanase, which produces exclusively xylobiose from oat spelt and birch xylans, was isolated from the culture medium of Aeromonas caviae ME-1. The enzyme (xylanase V) was purified by ammonium sulfate fractionation, hydrophobic interaction, and ion-exchange and gel filtration chromatographies. The homogeneity of the final preparation was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and agarose gel electrofocusing. The molecular mass and isoelectric point of the xylanase were 46 kDa and 5.4, respectively. Xylanase V had a maximum activity at a pH of 6.8 and at a temperature between 30 and 37°C. It was relatively stable at a pH between 5.0 and 8.6 and a temperature between 25 and 37°C. When soluble birch xylan was used as the substrate, the enzyme had a Km and Vmax of 2 mg/ml and 182 μmol of xylose equivalent liberated · min-1 · mg of protein-1, respectively. By the action of xylanase V on xylans (from oat spelt and birch), only one product corresponding ...

Research paper thumbnail of Allosteric regulation accompanied by oligomeric state changes of Trypanosoma brucei GMP reductase through cystathionine-β-synthase domain

Nature Communications, Apr 15, 2020

Guanosine 5′-monophosphate reductase (GMPR) is involved in the purine salvage pathway and is cons... more Guanosine 5′-monophosphate reductase (GMPR) is involved in the purine salvage pathway and is conserved throughout evolution. Nonetheless, the GMPR of Trypanosoma brucei (TbGMPR) includes a unique structure known as the cystathionine-β-synthase (CBS) domain, though the role of this domain is not fully understood. Here, we show that guanine and adenine nucleotides exert positive and negative effects, respectively, on TbGMPR activity by binding allosterically to the CBS domain. The present structural analyses revealed that TbGMPR forms an octamer that shows a transition between relaxed and twisted conformations in the absence and presence of guanine nucleotides, respectively, whereas the TbGMPR octamer dissociates into two tetramers when ATP is available instead of guanine nucleotides. These findings demonstrate that the CBS domain plays a key role in the allosteric regulation of TbGMPR by facilitating the transition of its oligomeric state depending on ligand nucleotide availability.

Research paper thumbnail of Flavin protein of trypanosoma cruzi, method of screening vermicide with the use of the same and diagnostic

Research paper thumbnail of Novel antimalarial agent

Research paper thumbnail of 105(P-46) キノン型ジテルペンの抗トリパノソーマ作用機構(ポスター発表の部)

天然有機化合物討論会講演要旨集, Sep 1, 2003

Research paper thumbnail of Crystallization and preliminary X-ray diffraction analysis of prostaglandin F 2α synthase from Trypanosoma brucei

Research paper thumbnail of Novel Characteristics of Trypanosoma brucei Guanosine 5'-monophosphate Reductase Distinct from Host Animals

PLoS neglected tropical diseases, 2016

The metabolic pathway of purine nucleotides in parasitic protozoa is a potent drug target for tre... more The metabolic pathway of purine nucleotides in parasitic protozoa is a potent drug target for treatment of parasitemia. Guanosine 5'-monophosphate reductase (GMPR), which catalyzes the deamination of guanosine 5'-monophosphate (GMP) to inosine 5'-monophosphate (IMP), plays an important role in the interconversion of purine nucleotides to maintain the intracellular balance of their concentration. However, only a few studies on protozoan GMPR have been reported at present. Herein, we identified the GMPR in Trypanosoma brucei, a causative protozoan parasite of African trypanosomiasis, and found that the GMPR proteins were consistently localized to glycosomes in T. brucei bloodstream forms. We characterized its recombinant protein to investigate the enzymatic differences between GMPRs of T. brucei and its host animals. T. brucei GMPR was distinct in having an insertion of a tandem repeat of the cystathionine β-synthase (CBS) domain, which was absent in mammalian and bacteria...

Research paper thumbnail of Artemisinins in the clinical and veterinary management of kinetoplastid infections

Research paper thumbnail of Artemisinins in the Clinical and Veterinary Management of Kinetoplastid Infextions

Research paper thumbnail of Crystallization and preliminary X-ray crystallographic studies of Trypanosoma brucei prostaglandin F2α synthase

Journal of Biochemistry, 2002

Research paper thumbnail of Xylanase IV, an Exoxylanase of Aeromonas caviae ME-1 Which Produces Xylotetraose as the Only Low-Molecular-Weight Oligosaccharide from Xylan

Applied and environmental microbiology, 1995

A novel xylanase (xylanase IV) which produces xylotetraose as the only low-molecular-weight oligo... more A novel xylanase (xylanase IV) which produces xylotetraose as the only low-molecular-weight oligosaccharide from oat spelt xylan was isolated from the culture medium of Aeromonas caviae ME-1. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the xylanase IV molecular weight was 41,000. Xylanase IV catalyzed the hydrolysis of oat spelt xylan, producing exclusively xylotetraose. The acid hydrolysate of the product gave d-xylose. The enzyme did not hydrolyze either p-nitrophenyl-(beta)-d-xyloside, small oligosaccharides (xylobiose and xylotetraose), or polysaccharides, such as starch, cellulose, carboxymethyl cellulose, laminarin, and (beta)-1,3-xylan.

Research paper thumbnail of Abkhazian crisis: from the Concept of Awareness of Common Threats to the Building of an "Abkhazian Security Community

Grani, 2020

This article is part of a research conducted as part of the Support Program for Doctoral Studies ... more This article is part of a research conducted as part of the Support Program for Doctoral Studies of Shota Rustaveli Georgian National Science Foundation.This article is part of a research conducted as part of the Support Program for Doctoral Studies of Shota Rustaveli Georgian National Science Foundation.Name of the research – "Interdisciplinary analysis of the complex system of the Abkhazian conflict by the method 4D-RAV-17" (grant number – PHDF‐18‐1147). The method is a combination of well-known and innovative approaches and techniques. This article is part of the abovementioned research. The complex system of the Abkhazian conflict in this article received a conditional definition – the Abkhazian crisis. The political component of the complex system is accordingly called the Abkhazian political crisis and is the main object of research in the framework of the article.The article is aimed at solving a specific scientific and applied task – at determining a scientifically...

Research paper thumbnail of Structural and Mutational Analysis of Trypanosoma brucei Prostaglandin H2 Reductase Provides Insight into the Catalytic Mechanism of Aldo-ketoreductases

Journal of Biological Chemistry, 2005

Research paper thumbnail of New anti-malarial phenylpropanoid conjugated iridoids from Morinda morindoides

Bioorganic & Medicinal Chemistry Letters, 2010

Research paper thumbnail of Structure and mutational analysis of Trypanosoma brucei prostaglandin F 2α synthase

Acta Crystallographica Section A Foundations of Crystallography, 2005

Trypanosoma brucei prostaglandin (PG) F 2 synthase (TbPGFS), an aldo-keto reductase, catalyzes th... more Trypanosoma brucei prostaglandin (PG) F 2 synthase (TbPGFS), an aldo-keto reductase, catalyzes the NADPH-dependent reduction of the endoperoxide moiety of PGH 2 to PGF 2. The overproduction of PGF 2 during trypanosomasis causes miscarriage in infected subjects. Here we report the crystal structures of TbPGFS-NADP + bounds citrate or sulfate at 2.1 Å and 2.6 Å resolution respectively. TbPGFS adopts a parallel (/) 8-barrel folds lacking the protrudent loops. The core active site structure is hydrophobic to bind hydrophobic substrates and contains tyrosine, lysine, histidine and aspartate known as a catalytic tetrad which is preserved in most of other aldo-keto reductases. These four residues are said to be indispensable for the reduction of PGH 2 , but mutagenesis shows that Tyr52 and Asp47 are not involved in the enzyme reaction and identifies His110 and Lys77 work as catalytic dyad. His 110 acts as a general acid catalyst, while Lys 77 facilitates proton donation by His 110 through a water molecule and forms a salt-bridge to stabilize the Asp 47 that binds NADPH. By comparing the citrate and sulfate complex structure, we detected that Trp187 holds the nicotinamide ring of NADPH from tilting on the access of PGH 2. These findings reveal a novel catalytic mechanism for the biological reduction of the endoperoxide PGH 2 by an aldo-keto reductase. The structure should allow for rational design of specific inhibitors useful to investigate the physiological roles of TbPGFS in trypanosomes.

Research paper thumbnail of Differentiation and apoptosis in the sleeping sickness inducing parasite Trypanosoma brucei

Eukaryotic parasites still cause fatal diseases (malaria, sleeping sickness, Kala Azar, Chagas di... more Eukaryotic parasites still cause fatal diseases (malaria, sleeping sickness, Kala Azar, Chagas disease etc.) which costs millions of deaths yearly and are hard to control because of insufficient drugs and fast developing resistance mechanisms. We investigate life cycle progression and differentiation processes in Trypanosoma brucei, the causative agent of sleeping sickness. Our results show that this parasite despite of being a protozoan, behaves as a concerted population which communicates by small signalling molecules. Slender parasites are rapidly dividing and thus responsible for the observed increase of parasitemia. They constantly produce a factor of unknown chemical structure, which at a certain cell density reaches a threshold concentration and triggers formation of metabolic and morphological changes within the parasite, thus leading to stumpy form trypanosomes. These are cell cycle arrested and very sensitive against prostaglandin D2, which is also produced by trypanosomes...

Research paper thumbnail of 105(P-46) キノン型ジテルペンの抗トリパノソーマ作用機構(ポスター発表の部)

Research paper thumbnail of Allosteric regulation accompanied by oligomeric state changes of Trypanosoma brucei GMP reductase through cystathionine-β-synthase domain

Nature Communications

Guanosine 5′-monophosphate reductase (GMPR) is involved in the purine salvage pathway and is cons... more Guanosine 5′-monophosphate reductase (GMPR) is involved in the purine salvage pathway and is conserved throughout evolution. Nonetheless, the GMPR of Trypanosoma brucei (TbGMPR) includes a unique structure known as the cystathionine-β-synthase (CBS) domain, though the role of this domain is not fully understood. Here, we show that guanine and adenine nucleotides exert positive and negative effects, respectively, on TbGMPR activity by binding allosterically to the CBS domain. The present structural analyses revealed that TbGMPR forms an octamer that shows a transition between relaxed and twisted conformations in the absence and presence of guanine nucleotides, respectively, whereas the TbGMPR octamer dissociates into two tetramers when ATP is available instead of guanine nucleotides. These findings demonstrate that the CBS domain plays a key role in the allosteric regulation of TbGMPR by facilitating the transition of its oligomeric state depending on ligand nucleotide availability.

Research paper thumbnail of Aeromonas caviae ME-1 xylanases : biochemical studies, biotechnological utilization and analysis of xylanase(s) gene

Research paper thumbnail of Evidence of Prostaglandin Production by the Human Malaria Parasite, Plasmodium Falciparum

South African Journal of Science, 1998

Research paper thumbnail of Purification and Characterization of Aeromonas caviae ME-1 Xylanase V, Which Produces Exclusively Xylobiose from Xylan

A xylanase, which produces exclusively xylobiose from oat spelt and birch xylans, was isolated fr... more A xylanase, which produces exclusively xylobiose from oat spelt and birch xylans, was isolated from the culture medium of Aeromonas caviae ME-1. The enzyme (xylanase V) was purified by ammonium sulfate fractionation, hydrophobic interaction, and ion-exchange and gel filtration chromatographies. The homogeneity of the final preparation was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and agarose gel electrofocusing. The molecular mass and isoelectric point of the xylanase were 46 kDa and 5.4, respectively. Xylanase V had a maximum activity at a pH of 6.8 and at a temperature between 30 and 37°C. It was relatively stable at a pH between 5.0 and 8.6 and a temperature between 25 and 37°C. When soluble birch xylan was used as the substrate, the enzyme had a Km and Vmax of 2 mg/ml and 182 μmol of xylose equivalent liberated · min-1 · mg of protein-1, respectively. By the action of xylanase V on xylans (from oat spelt and birch), only one product corresponding ...

Research paper thumbnail of Allosteric regulation accompanied by oligomeric state changes of Trypanosoma brucei GMP reductase through cystathionine-β-synthase domain

Nature Communications, Apr 15, 2020

Guanosine 5′-monophosphate reductase (GMPR) is involved in the purine salvage pathway and is cons... more Guanosine 5′-monophosphate reductase (GMPR) is involved in the purine salvage pathway and is conserved throughout evolution. Nonetheless, the GMPR of Trypanosoma brucei (TbGMPR) includes a unique structure known as the cystathionine-β-synthase (CBS) domain, though the role of this domain is not fully understood. Here, we show that guanine and adenine nucleotides exert positive and negative effects, respectively, on TbGMPR activity by binding allosterically to the CBS domain. The present structural analyses revealed that TbGMPR forms an octamer that shows a transition between relaxed and twisted conformations in the absence and presence of guanine nucleotides, respectively, whereas the TbGMPR octamer dissociates into two tetramers when ATP is available instead of guanine nucleotides. These findings demonstrate that the CBS domain plays a key role in the allosteric regulation of TbGMPR by facilitating the transition of its oligomeric state depending on ligand nucleotide availability.

Research paper thumbnail of Flavin protein of trypanosoma cruzi, method of screening vermicide with the use of the same and diagnostic

Research paper thumbnail of Novel antimalarial agent

Research paper thumbnail of 105(P-46) キノン型ジテルペンの抗トリパノソーマ作用機構(ポスター発表の部)

天然有機化合物討論会講演要旨集, Sep 1, 2003

Research paper thumbnail of Crystallization and preliminary X-ray diffraction analysis of prostaglandin F 2α synthase from Trypanosoma brucei

Research paper thumbnail of Novel Characteristics of Trypanosoma brucei Guanosine 5'-monophosphate Reductase Distinct from Host Animals

PLoS neglected tropical diseases, 2016

The metabolic pathway of purine nucleotides in parasitic protozoa is a potent drug target for tre... more The metabolic pathway of purine nucleotides in parasitic protozoa is a potent drug target for treatment of parasitemia. Guanosine 5'-monophosphate reductase (GMPR), which catalyzes the deamination of guanosine 5'-monophosphate (GMP) to inosine 5'-monophosphate (IMP), plays an important role in the interconversion of purine nucleotides to maintain the intracellular balance of their concentration. However, only a few studies on protozoan GMPR have been reported at present. Herein, we identified the GMPR in Trypanosoma brucei, a causative protozoan parasite of African trypanosomiasis, and found that the GMPR proteins were consistently localized to glycosomes in T. brucei bloodstream forms. We characterized its recombinant protein to investigate the enzymatic differences between GMPRs of T. brucei and its host animals. T. brucei GMPR was distinct in having an insertion of a tandem repeat of the cystathionine β-synthase (CBS) domain, which was absent in mammalian and bacteria...

Research paper thumbnail of Artemisinins in the clinical and veterinary management of kinetoplastid infections

Research paper thumbnail of Artemisinins in the Clinical and Veterinary Management of Kinetoplastid Infextions

Research paper thumbnail of Crystallization and preliminary X-ray crystallographic studies of Trypanosoma brucei prostaglandin F2α synthase

Journal of Biochemistry, 2002

Research paper thumbnail of Xylanase IV, an Exoxylanase of Aeromonas caviae ME-1 Which Produces Xylotetraose as the Only Low-Molecular-Weight Oligosaccharide from Xylan

Applied and environmental microbiology, 1995

A novel xylanase (xylanase IV) which produces xylotetraose as the only low-molecular-weight oligo... more A novel xylanase (xylanase IV) which produces xylotetraose as the only low-molecular-weight oligosaccharide from oat spelt xylan was isolated from the culture medium of Aeromonas caviae ME-1. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the xylanase IV molecular weight was 41,000. Xylanase IV catalyzed the hydrolysis of oat spelt xylan, producing exclusively xylotetraose. The acid hydrolysate of the product gave d-xylose. The enzyme did not hydrolyze either p-nitrophenyl-(beta)-d-xyloside, small oligosaccharides (xylobiose and xylotetraose), or polysaccharides, such as starch, cellulose, carboxymethyl cellulose, laminarin, and (beta)-1,3-xylan.