Stereospecificity of Thermostable Ornithine 5-Aminotransferase for the Hydrogen Transfer in the L- and D-Ornithine Transamination (MOLECULAR BIOFUNCTION-Molecular Microbial Science)

The thermostable ornithine 5-aminotransferase of a thermophile, Bacillus sp. YM-2 is unique in acting on both enantiomers of ornithine, although less effectively on the D-enantiomer. We studied the stereospecificity of the enzyme for the hydrogen abstraction from C-5 of the substrate moiety and the addition and removal of the hydrogen at C-4' of the cofactor (pyridoxal phosphate and pyridoxamine phosphate) moiety of the external Schiff base intermediate in the transamination of L- and D-ornithine. [5- 3H]L- and D-ornithines were prepared by incubation of L- and D-ornithines with the B. sp. YM-2 ornithine 5-aminotransferase in 3H2O, respectively. The C-5 of the tritiated L-and D-ornithine was proved to have the S-configuration with L-ornithine 5-aminotransferase of a mesophile, Bacillus sphaericus, catalyzing the stereospecific abstraction of pro-S hydrogen from C-5 of L-ornithine and amino acid racemase with lowsubstrate specificity of Pseudomonas putida . When apo-form of the enzyme was incubated with pyridoxamine 5'-phosphates that was stereospecifically tritiated at C-4' and 2-oxoglutarate in the presence of L-ornithine or D-ornithine, tritium was released exclusively from (4'S)-[4'-3H] pyridoxamine. These results suggest that the B. sp. YM-2 ornithine 5-aminotransferase stereospecifically abstracts the pro-S hydrogen from C-5 of L- and D-ornithine. The hydrogen abstracted is then transferred to C-4' of the cofactor moiety stereospecifically on the si face of the external Schiff base intermediate irrespective of the C-2 configuration of amino donor

Effect of few-walled carbon nanotube crystallinity on electron field emission property

We discuss the influence of few-walled carbon nanotubes (FWCNTs) treated with nitric acid and/or sulfuric acid on field emission characteristics. FWCNTs/tetraethyl orthosilicate (TEOS) thin film field emitters were fabricated by a spray method using FWCNTs/TEOS sol one-component solution onto indium tin oxide (ITO) glass. After thermal curing, they were found tightly adhered to the ITO glass, and after an activation process by a taping method, numerous FWCNTs were aligned preferentially in the vertical direction. Pristine FWCNT/ TEOS-based field emitters revealed higher current density, lower turn-on field, and a higher field enhancement factor than the oxidized FWCNTs-based field emitters. However, the unstable dispersion of pristine FWCNT in TEOS/N,N-dimethylformamide solution was not applicable to the field emitter fabrication using a spray method. Although the field emitter of nitric acid-treated FWCNT showed slightly lower field emission characteristics, this could be improved by the introduction of metal nanoparticles or resistive layer coating. Thus, we can conclude that our spray method using nitric acid-treated FWCNT could be useful for fabricating a field emitter and offers several advantages compared to previously reported techniques such as chemical vapor deposition and screen printing.ope

Zizania latifolia and Its Major Compound Tricin Regulate Immune Responses in OVA-Treated Mice

Tricin, a flavone belonging to the Gramineae family, has been confirmed to be the primary compound in a Zizania latifolia extract (ZLE) that prevents allergies. Various allergic reactions occur because of the unbalanced differentiation of T help cells (Th) and the consequent overproduction of IgE. Therefore, the regulation of Th1 and Th2 responses by T helper cell differentiation is essential for suppressing allergic responses. This study confirmed the immunomodulatory effects of ZLE and the major compound tricin in an OVA-sensitized mouse model. The IgE and OVA-specific production of tricin and ZLE in plasma were investigated in OVA-sensitized mice. The effects of tricin and ZLE on the amount of Th1 and Th2 cytokines and transcription factors released in splenocytes were investigated in OVA-sensitized mice. The skin roughness and the number of mast cells were confirmed by staining the skin surface with H&E and toluidine blue. Tricin and ZLE reduced the plasma IgE and OVA-specific-IgE levels significantly compared to the OVA group. On the other hand, tricin and ZLE promoted the release of the Th1 cytokines IL-12 and IFN-γ and inhibited the release of Th2 cytokines (IL-4, -10, -13, and -5) in OVA-sensitized mice. Tricin and ZLE induced T-bet and NFATc2 expression, and-down regulated GATA-3 levels. The skin roughness and the number of mast cells decreased in the OVA-immunized mice. Overall, the data indicate that tricin and ZLE may prevent allergy-related diseases through immunomodulation

Tricin Isolated from Enzyme-Treated Zizania latifolia Extract Inhibits IgE-Mediated Allergic Reactions in RBL-2H3 Cells by Targeting the Lyn/Syk Pathway

Tricin, a flavone present in rice bran, is confirmed as the major efficacious compound present in the enzyme-treated Zizania latifolia extract (ETZL), which protects against UVB-induced skin-aging. However, the suppressive mechanism of tricin on allergic responses remains unknown. The present study, therefore, aimed to determine the mechanisms of tricin and ETZL on mast cell degranulation in IgE-activated rat basophilic leukemia cell line (RBL-2H3) cells. We investigated the regulatory effects of tricin and ETZL on degranulation, production of cytokines and lipid mediators, and signaling proteins involved in the IgE-bound high-affinity IgE receptor activation, mitogen-activated protein kinase, arachidonic acid and Syk. The production of β–hexosaminidase, tumor necrosis factor-α, interleukin-4, leukotrienes (LT) B4, LTC4 and prostaglandin E2 in IgE-stimulated RBL-2H3 cells were significantly inhibited by exposure to tricin or ETZL. Moreover, tricin and ETZL inhibit the phosphorylation of cytosolic phospholipase A2, 5-lipoxygenase and cyclooxygenase-2. Furthermore, the phosphorylation of Akt, ERK, p38, JNK, protein kinase Cδ and phospholipase Cγ1 were effectively suppressed by both samples. Exposure to tricin or ETZL also significantly decreases the phosphorylation of Lyn and Syk, but has minimal effect on Fyn. Taken together, our data indicate that tricin and ETZL are potential anti-allergic materials that could be applied for the prevention of allergy-related diseases

Protection against UVB-Induced Wrinkle Formation in SKH-1 Hairless Mice: Efficacy of Tricin Isolated from Enzyme-Treated Zizania latifolia Extract

Tricin, a flavone found mainly in rice bran and sugarcane, has various beneficial effects. It has proven to be a clinically safe and selective potent inhibitor of different cancer cell lines. In this study, we evaluated the efficacy of enzyme-treated Zizania latifolia (ETZL) and its major active compound tricin on skin photoaging in SKH-1 hairless mice. Tricin (0.3 mg/kg) and ETZL (50, 150, and 300 mg/kg) were orally administrated to mice for 14 weeks; no cytotoxicity was observed during the entire experimental period. After UVB exposure, we observed significant increases in keratinization, coarse wrinkles, loss of moisture, thickened epidermis, and collagen fiber degradation in the dorsal skin. These features of photoaging were significantly suppressed after oral administration of tricin or ETZL. In addition, the protein expression of collagen effectively increased in ETZL (150 and 300 mg/kg)-treated mice, while the increased metalloproteinase (MMP)-1 and MMP-3 expressions were reduced after exposure to tricin or ETZL, although the effects were not dose-dependent. These data indicate that ETZL may be effective for attenuation of UVB-induced skin damage and photoaging in hairless mice, possibly by inhibiting MMPs expression