Mechanism for high stability of liposomal glucose oxidase to inhibitor hydrogen peroxide produced in prolonged glucose oxidation

Glucose oxidase (GO) was encapsulated in the liposomes composed of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) to increase the enzyme stability through its decreased inhibition because of hydrogen peroxide (H(2)O(2)) produced in the glucose oxidation. The GO-containing liposomes (GOLs) were completely free of the inhibition even in the complete conversion of 10 mM glucose at 25 degrees C because the H(2)O(2) concentration was kept negligibly low both outside and inside liposomes throughout the reaction. It was interestingly revealed that the H(2)O(2) produced was decomposed not only by a slight amount of catalase originally contained in the commercially available GO but also by the lipid membranes of GOL. As compared to the GOL-catalyzed reaction, the free GO-catalyzed reaction more highly accumulated H(2)O(2) because of the more rapid glucose conversion despite containing free catalase, leading to the completely inhibited GO before reaching a sufficient glucose conversion. This suggested that only the liposomal catalase could continue to catalyze the H(2)O(2) decomposition. The effect of the glucose oxidation rate, i.e., the H(2)O(2) production rate on the liposomal GO inhibition, was also examined employing the various GOLs with different permeabilities to glucose present in their external phase. It was concluded that the liposomal GO free of the inhibition could be obtained when the GOL-catalyzed H(2)O(2) formation rate was limited by such a suitable lipid bilayer as POPC membrane so that the rate was well-balanced with the sum of the above two H(2)O(2) decomposition rates. The highly stable GOL obtained in the present paper was shown to be a useful biocatalyst for the prolonged glucose oxidation.     

In vitro and in vivo stability of plasmids in attenuated Salmonella enterica serovar typhimurium used as a carrier of DNA vaccine is associated with its replication origin.

The ability of live attenuated Salmonella enterica serovar typhimurium (S. typhimurium) as a carrier of DNA vaccine was evaluated using model plasmid encoding beta-galactosidase (beta-Gal) and BALB/c mice. We constructed pBRCMVbeta, beta-Gal expression apparatus having a replication origin from low copy pBR322. Comparison of the plasmid stability showed that pBRCMVbeta remained stable in Salmonella even after oral administration, while pUC-based pCMVbeta tended to be lost quickly. However, titers for beta-Gal specific IgG in sera did not significantly increase in mice orally administered S. typhimurium harboring pBRCMVbeta. These data suggest that the stability of plasmid in S. typhimurium is associated with its replication origin. Further studies are required to scientifically establish this methodology.     

Design,synthesis, and evaluation of novel VEGFR2 kinase inhibitors: Discovery of [1,2,4]triazolo[1,5-a]pyridine derivatives with slow dissociation kinetics

For the purpose of discovering novel type-II inhibitors of vascular endothelial growth factor receptor 2 (VEGFR2) kinase, we designed and synthesized 5,6-fused heterocyclic compounds bearing a anilide group. A co-crystal structure analysis of imidazo[1,2-b]pyridazine derivative 2 with VEGFR2 revealed that the N1-nitrogen of imidazo[1,2-b]pyridazine core interacts with the backbone NH group of Cys919. To retain this essential interaction, we designed a series of imidazo[1,2-a]pyridine, [1,2,4]triazolo[1,5-a]pyridine, thiazolo[5,4-b]pyridine, and 1,3-benzothiazole derivatives maintaining a ring nitrogen as hydrogen bond acceptor (HBA) at the corresponding position. All compounds thus designed displayed strong inhibitory activity against VEGFR2 kinase, and the [1,2,4]triazolo[1,5-a]pyridine 13d displayed favorable physicochemical properties. Furthermore, 13d inhibited VEGFR2 kinase with slow dissociation kinetics and also inhibited platelet-derived growth factor receptor (PDGFR) kinases. Oral administration of 13d showed potent anti-tumor efficacy in DU145 and A549 xenograft models in nude mice.     

Discovery of N-[5-({2-[(cyclopropylcarbonyl)amino]imidazo[1,2-b]pyridazin-6-yl}oxy)-2-methylphenyl]-1,3-dimethyl-1H-pyrazole-5-carboxamide (TAK-593), a highly potent VEGFR2 kinase inhibitor

Vascular endothelial growth factor (VEGF) plays important roles in tumor angiogenesis, and the inhibition of its signaling pathway is considered an effective therapeutic option for the treatment of cancer. In this study, we describe the design, synthesis, and biological evaluation of 2-acylamino-6-phenoxy-imidazo[1,2-b]pyridazine derivatives. Hybridization of two distinct imidazo[1,2-b]pyridazines 1 and 2, followed by optimization led to the discovery of N-[5-({2-[(cyclopropylcarbonyl)amino]imidazo[1,2-b]pyridazin-6-yl}oxy)-2-methylphenyl]-1,3-dimethyl-1H-pyrazole-5-carboxamide (23a, TAK-593) as a highly potent VEGF receptor 2 kinase inhibitor with an IC₅₀ value of 0.95 nM. The compound 23a strongly suppressed proliferation of VEGF-stimulated human umbilical vein endothelial cells with an IC₅₀ of 0.30 nM. Kinase selectivity profiling revealed that 23a inhibited platelet-derived growth factor receptor kinases as well as VEGF receptor kinases. Oral administration of 23a at 1 mg/kg bid potently inhibited tumor growth in a mouse xenograft model using human lung adenocarcinoma A549 cells (T/C = 8%).     

Magnetic Resonance Findings of the Corpus Callosum in Canine and Feline Lysosomal Storage Diseases

Several reports have described magnetic resonance (MR) findings in canine and feline lysosomal storage diseases such as gangliosidoses and neuronal ceroid lipofuscinosis. Although most of those studies described the signal intensities of white matter in the cerebrum, findings of the corpus callosum were not described in detail. A retrospective study was conducted on MR findings of the corpus callosum as well as the rostral commissure and the fornix in 18 cases of canine and feline lysosomal storage diseases. This included 6 Shiba Inu dogs and 2 domestic shorthair cats with GM1 gangliosidosis; 2 domestic shorthair cats, 2 familial toy poodles, and a golden retriever with GM2 gangliosidosis; and 2 border collies and 3 chihuahuas with neuronal ceroid lipofuscinoses, to determine whether changes of the corpus callosum is an imaging indicator of those diseases. The corpus callosum and the rostral commissure were difficult to recognize in all cases of juvenile-onset gangliosidoses (GM1 gangliosidosis in Shiba Inu dogs and domestic shorthair cats and GM2 gangliosidosis in domestic shorthair cats) and GM2 gangliosidosis in toy poodles with late juvenile-onset. In contrast, the corpus callosum and the rostral commissure were confirmed in cases of GM2 gangliosidosis in a golden retriever and canine neuronal ceroid lipofuscinoses with late juvenile- to early adult-onset, but were extremely thin. Abnormal findings of the corpus callosum on midline sagittal images may be a useful imaging indicator for suspecting lysosomal storage diseases, especially hypoplasia (underdevelopment) of the corpus callosum in juvenile-onset gangliosidoses.     

Isolation and primary structure of a cellulase from the Japanese sea urchin Strongylocentrotus nudus

Glycoside-hydrolase-family 9 (GHF9) cellulases are known to be widely distributed in metazoa. These enzymes have been appreciably well investigated in protostome invertebrates such as arthropods, nematodes, and mollusks but have not been characterized in deuterostome invertebrates such as sea squirts and sea urchins. In the present study, we isolated the cellulase from the Japanese purple sea urchin Strongylocentrotus nudus and determined its enzymatic properties and primary structure. The sea urchin enzyme was extracted from the acetone-dried powder of digestive tract of S. nudus and purified by conventional chromatographies. The purified enzyme, which we named SnEG54, showed a molecular mass of 54kDa on SDS-PAGE and exhibited high hydrolytic activity toward carboxymethyl cellulose with an optimum temperature and pH at 35 degrees C and 6.5, respectively. SnEG54 degraded cellulose polymer and cellooligosaccharides larger than cellotriose producing cellotriose and cellobiose but not these small cellooligosaccharides. From a cDNA library of the digestive tract we cloned 1822-bp cDNA encoding the amino-acid sequence of 444 residues of SnEG54. This sequence showed 50-57% identity with the sequences of GHF9 cellulases from abalone, sea squirt, and termite. The amino-acid residues crucial for the catalytic action of GHF9 cellulases are completely conserved in the SnEG54 sequence. An 8-kbp structural gene fragment encoding SnEG54 was amplified by PCR from chromosomal DNA of S. nudus. The positions of five introns are consistent with those in other animal GHF9 cellulase genes. Thus, we confirmed that the sea urchin produces an active GHF9 cellulase closely related to other animal cellulases.     

The physiological role of riboflavin transporter and involvement of FMN-riboswitch in its gene expression in Corynebacterium glutamicum

Riboflavin is a precursor of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which work as cofactors of numerous enzymes. Understanding the supply system of these cofactors in bacteria, particularly those used for industrial production of value added chemicals, is important given the pivotal role the cofactors play in substrate metabolism. In this work, we examined the effect of disruption of riboflavin utilization genes on cell growth, cytoplasmic flavin levels, and expression of riboflavin transporter in Corynebacterium glutamicum. Disruption of the ribA gene that encodes bifunctional GTP cyclohydrolase II/3,4-dihydroxy-2-butanone 4-phosphate synthase in C. glutamicum suppressed growth in the absence of supplemental riboflavin. The growth was fully recovered upon supplementation with 1 μM riboflavin, albeit at reduced intracellular concentrations of FMN and FAD during the log phase. Concomitant disruption of the ribA and ribM gene that encodes a riboflavin transporter exacerbated supplemental riboflavin requirement from 1 μM to 50 μM. RibM expression in FMN-rich cells was about 100-fold lower than that in FMN-limited cells. Mutations in putative FMN-riboswitch present immediately upstream of the ribM gene abolished the FMN response. This 5′UTR sequence of ribM constitutes a functional FMN-riboswitch in C. glutamicum.