1990 Fiscal Year Final Research Report Summary
Induction of an NADH-quinone reductase which alleviate menadione toxicity in Escherichia coli.
| Project/Area Number |
01571195
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Biological pharmacy
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| Research Institution | Chiba University |
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Principal Investigator |
UNEMOTO Tsutomu Chiba University, Faculty of Pharmaceutical Sciences, Professor, 薬学部, 教授 (30089601)
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| Co-Investigator(Kenkyū-buntansha) |
HAYASHI Maki Chiba University, Faculty of Pharmaceutical Sciences, Associate Professor, 薬学部, 助教授 (50092086)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Menadione / NADH-quinone reductase / Induction / DT-Diaphorase / Quinone toxicity / E. coli / Oxygen stress / Quinone metabolism |
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| Research Abstract |
It was found that when Escherichia coli is grown in the presence of 0.2-0.3 mM menadione (2-methyl-1, 4-naphthoquinone), an FMN-dependent NADH-quinonereducase increases more than 20-fold in the cytoplasmic fraction. The menadion-induced quinone reductase was isolated from the cyto plasmic fraction of induced cells. The purified enzyme had an Mr of 24 kDa on SDS-polyacrylamide gel electrophoresis. The enzyme required flavin as a cofactor and a half-maximum activity was obtained with 0.54 muM FMN or 16.5 muM FAD. The enzyme had a broad pH optimum at pH 7.0-8.0 and reacted with NADH, but not with NADPH. The reaction followed a ping-pong mechanism and the intrinsic Km values for NADA and menadione were estimated to be 132 muM and 2.0 muM, respectively. Dicoumarol was a simple competitive inhibitor with respect to NADH with a Ki value of 0.22 muM. The electron acceptor specificity of this enzyme was very similar to that of NAD (P) H : (quinone acceptor) oxidoreductase (EC1.6.99.2, DT-diaphorase) from rat liver. Since menadione is reduced by the two-electron reduction pathway to menadiol, The induction of this enzyme is likely to be an adaptive response of E. coli to partially alleviate the toxicity of menadione.
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