Takashi Komiya

Inhibition of eukaryotic DNA polymerase α by persimmon (Diospyros kaki) extract and related polyphenols

The effects of persimmon extract (Diospyros kaki) and related polyphenols on eukaryotic DNA polymerase α were examined. It was found that persimmon extract, epigallocatechin gallate, and epicatechin gallate strongly inhibited the activity of DNA polymerase α purified from calf thymus. Among these polyphenols, persimmon extract had the most potent effect on DNA polymerase α activity and the concentration of persimmon extract producing 50% inhibition of the activity was 0.191 μM. Persimmon extract showed a weaker effect on DNA polymerase β and slightly inhibited primase and DNA polymerase I. The inhibition of DNA polymerase α by persimmon extract was competitive with the template‐primer and noncompetitive with dTTP substrate. The Ki value of DNA polymerase α for persimmon extract was estimated to be 70 nM. Moreover, persimmon extract inhibited [3H]thymidine incorporation of human peripheral lymphocyte cells stimulated by PHA.

Studies on the Screening of Lactic Acid Bacteria Suitable for Hyposalt-pickles and Their Fermentation Conditions

発酵漬物の製造において,乳酸菌を添加した漬物を検討した.スターターカルチャー用乳酸菌の選択と発酵条件について,以下のような結果を得た.(1) 36株の乳酸菌から発酵漬物に適したものを検索したところ,生育速度が速いこと,好ましい酸味や香りを生産することなどから,8菌株を選択した.(2) 最も好ましい香気を生成した,Leuconostoc paramesenteroides DA-1株について性質を検討した結果,最適発酵温度は10°Cで,食塩0∼3%,グルコース無添加のモデル漬物中でよく発酵した.(3) 大根を用いて低食塩の漬物を調製した結果,Leuc.DA-1株を接種することで,腐敗や変色がおこらず,梅酢様の良好な香気,うま味を生成した.