Suk Bai

Platelet-activating factor induces matrix metalloproteinase-9 expression through Ca2+- or PI3K-dependent signaling pathway in a human vascular endothelial cell line

Platelet‐activating factor (PAF) augments angiogenesis by promoting the synthesis of a variety of angiogenic factors, via the nuclear factor (NF)‐κB activation. Recently, we reported that PAF upregulates MMP‐9 expression in a NF‐κB‐dependent manner. In this study, we investigated the signaling pathway involved in PAF‐induced MMP‐9 expression in ECV304 cells. Our current data indicate that the Ca2+‐ or phosphatidylinositol 3‐kinase (PI3K)‐dependent signaling pathway is necessary for PAF‐induced MMP‐9 expression. Furthermore, PAF‐induced NF‐κB activation was blocked by selective inhibitors of Ca2+, PI3K, or extracellular signal‐regulated kinase (ERK). Our results suggest that PAF‐induced MMP‐9 expression, in a NF‐κB‐dependent manner, is regulated by Ca2+, PI3K and ERK signaling pathways.

Cloning, expression and nucleotide sequences of two xylanase genes from Paenibacillus sp.

Two genes, xynA and xynB, encoding xylanases from Paenibacillus sp. KCTC 8848P were cloned and expressed in Escherichia coli, and their nucleotide sequences were determined. The xylanases of E. coli transformants were released into the extracellular culture fluid in the absence of xylan. The structural gene of xynA 636 bp, encoded a protein of 212 amino acids, while the xynB gene consisted of 951 bp open reading frame for a protein of 317 amino acids. The amino acid sequence of the xynAgene showed 83% similarity to the xylanase of Aeromonas caviae, and belonged to the family 11 glycosyl hydrolases. The deduced amino acid sequence of the xynB gene, however, showed 51% similarity to the xylanase of Rhodothermus marinus, and belonged to the family 10 glycosyl hydrolases.

Construction of an amylolytic industrial strain of Saccharomyces cerevisiae containing the Schwanniomyces occidentalis α-amylase gene

The gene encoding Schwanniomyces occidentalis α-amylase (AMY) was introduced into the chromosomal δ sequences of an industrial strain of Saccharomyces cerevisiae. To obtain a strain suitable for commercial use, an δ-integrative cassette devoid of bacterial DNA sequences was constructed that contains the AMY gene and aureobasidin A resistance gene (AUR1-C) as the selection marker. The AMY gene was expressed under the control of the alcohol dehydrogenase gene promoter (ADC1p). The α-amylase activity of Sacc. cerevisiae transformed with this integrative cassette was 6 times higher than that of Sch. occidentalis. The transformants (integrants) were mitotically stable after 100 generations in nonselective medium.

Construction of an industrial polyploid strain of Saccharomyces cerevisiae containing Saprolegnia ferax β-amylase gene and secreting β-amylase

An industrial polyploid strain of Saccharomyces cerevisiae containing Saprolegnia ferax β-amylase gene was developed by using two yeast integrating plasmids. One plasmid was constructed that contains the geneticin resistance gene (Gtr) as the selection marker and the ribosomal DNA (rDNA) portion that comprises the 18S rDNA as the recombination site. The other plasmid contains the aureobasidin A resistance gene (AUR1-C) as the selection marker and the chromosomal Ty δ sequence as the recombination site. The β-amylase activity of one clone of Saccharomyces cerevisiae transformed sequentially with these two plasmids was approx. 9 times higher than that of Saprolegnia ferax. This type of integration was mitotically stable even after 100 generations of cell multiplication under non-selective conditions.

A gene encoding Achlya bisexualis β-amylase and its expression in Saccharomyces cerevisiae

Part of a β-amylase genomic DNA sequence from the oomycete, Achlya bisexualis was cloned by polymerase chain reaction (PCR) using degenerate oligonucleotide primers derived from the conserved regions of other known β-amylase sequences. The 5′- and 3′-regions of the β-amylase gene were amplified by genome walking method. The Ach. bisexualis β-amylase gene consisted of a 1338bp open reading frame, encoding a protein of 446 amino acids with a molecular weight of 49 381Da, and was not interrupted by any intron. The deduced amino acid sequence of the β-amylase gene had 67% similarity to the β-amylase of Saprolegnia ferax, followed by 40% similarity to that ofArabidopsis thaliana. The β-amylase gene was expressed in Saccharomyces cerevisiae placing it under the control of the alcohol dehydrogenase gene (ADC1) promoter.

Phytosynthesis of Silver and Gold Nanoparticles Using the Hot Water Extract of Mixed Woodchip Powder and Their Antibacterial Efficacy

This study investigates the phytosynthesis, characterization, and antibacterial efficacy of silver and gold nanoparticles (NPs) produced using the hot water extract of mixed woodchip powder. The woodchip extract (WCE) was successfully used as both a reducing and stabilizing agent for the phytosynthesis of both crystalline metal NPs. The effects of different physicochemical factors affecting the formation of the metal NPs including reaction pH, concentration of the precursor metal salts, amount of WCE, and external energy input were evaluated. The characterization of the metal NPs was performed by transmission electron microscopy, selected area electron diffraction (SAED), energy dispersive X-ray (EDX) spectroscopy, and X-ray diffraction (XRD) pattern analysis. In addition, the antibacterial efficacy of the phytosynthesized NPs was measured. The AgNPs showed clear antibacterial activity against four representative bacterial strains. However, the AuNPs did not exhibit bactericidal activity, probably due to their surface modifications and relatively large size. These results suggest that the phytosynthesis of the metal NPs using WCE is highly efficient, and its convenience makes it suitable for use in large-scale production.