Tae-Ick Mheen

Purification and characterization of a bacteriocin produced by Lactococcus lactis subsp. lactis H-559 isolated from kimchi.

Lactic acid bacteria were isolated from kimchi and screened for bacteriocin production. Strain H-559, identified as Lactococcus lactis subsp. lactis, exhibited the strongest antibacterial activity among them and was active against pathogenic bacteria such as Listeria monocytogenes and Staphylococcus aureus as well as many lactic acid bacteria. The antimicrobial substance produced by L. lactis subsp. lactis H-559 was inactivated by alpha-chymotrypsin, and protease type IX and XIV and was confirmed to be a bacteriocin. The bacteriocin activity was stable from pH 2.0-11.0 and up to 10 min heating at 100 degrees C. The bacteriocin was sequentially purified by ammonium sulfate precipitation, ion-exchange chromatography, and reversed-phase high-performance liquid chromatography (HPLC). Its molecular weight was determined to be 3343.7 Da by MALDI-mass spectrometry. Isoleucine was detected as the first N-terminal amino acid residue but the remaining amino acid sequence could not be determined by the Edman degradation method. It was different from other bacteriocins in terms of pH stability, molecular weight, amino acid composition, and the partial amino acid sequences of peptides obtained by acid hydrolysis.

Lactobacillus kimchii sp. nov., a new species from kimchi.

A bacteriocin-producing lactic acid bacterium, which was isolated from the Korean fermented-vegetable food kimchi, was subjected to a polyphasic taxonomic study using phenotypic characterization and phylogenetic and genetic methods. This organism (MT-1077T) has phenotypic properties that are consistent with the description characterizing the genus Lactobacillus. Phylogenetic analysis based on 16S rDNA sequences showed clearly that strain MT-1077T is a member of the genus Lactobacillus. The closest phylogenetic relatives are Lactobacillus alimentarius KCTC 3593T and Lactobacillus farciminis LMG 9200T, with levels of 16S rDNA similarity of 98.4 and 98.2%, respectively. Levels of 16S rDNA similarity between strain MT-1077T and other Lactobacillus species were less than 93.0%. Differences in some phenotypic characteristics and DNA-DNA relatedness data indicated that strain MT-1077T should be distinguished from L. alimentarius KCTC 3593T and L. farciminis LMG 9200T. On the basis of the data presented, it is proposed that strain MT-1077T should be placed in the genus Lactobacillus as a new species, Lactobacillus kimchii sp. nov. The type strain of the new species is strain MT-1077T (= KCTC 8903PT = JCM 10707T).

Inhibition of angiotensin II receptor binding by quinolone alkaloids from Evodia rutaecarpa

A biologically monitored fractionation of methanol extracts of the fruit of Evodia rutaecarpa led to the isolation of quinolone alkaloids, evocarpin (1), 1‐methyl‐2‐[(4Z,7Z)‐4,7‐tridecadienyl]‐4(1H)‐quinolone (2) and 1‐methyl‐2‐[(6Z,9Z)‐6,9‐pentadecadienyl]‐4(1H)‐quinolone (3) as blockers of angiotensin II receptor binding with IC50 values of 43.4 μM, 34.1 μM and 48.2 μM, respectively.

Involvement of SH2-SH2-SH3 domain of phospholipase Cγ1 in NF-κB signaling

To directly define the role of phospholipase Cγ1 (PLCγ1) in NF‐κB activation, NF‐κB promoted luciferase reporter gene plasmid (pNF‐κB‐Luc) was transfected into rat‐3Y1 fibroblasts that overexpress whole PLCγ1 (PLCγ1‐3Y1), src homology domains SH2‐SH2‐SH3 of PLCγ1 (SH223‐3Y1) and v‐src (Src‐3Y1). Transient transfection with pNF‐κB‐Luc remarkably increased the luciferase activity in all three transformants compared with normal rat‐3Y1 cells. Pretreatment with inhibitors of protein tyrosine kinase reduced this increase in luciferase activity, but U73122 (a PLC inhibitor) did not. While PD98059, an inhibitor of mitogen activated protein kinase (MAPK), significantly reduced the luciferase activity, there was no effect by wortmannin and Ro‐31‐8220, inhibitors of phosphatidylinositol 3‐kinase (PI3K) and protein kinase C (PKC), respectively. This study shows a direct evidence that the SH2‐SH2‐SH3 region of PLCγ1 contributes to the NF‐κB signaling and that MAPK, but not PI3K and PKC, is involved in SH2‐SH2‐SH3 mediated NF‐κB activation in these cells.