Beta hemolysis 유발 병원균 Bacillus cereus의 HQNO-sensitive NADH:DCIP oxidoreductase

Abstract

호기적으로 자란 Bacillus cereus KCTC 3674로 부터 조제된 막은 NADH만을 산화하고, deamino-NADH는 거의 산화하지 않았다. 호흡쇄와 연계된 NADH oxidase계는 <TEX>$K_m$</TEX> 값이 약 <TEX>$65\;{\mu}M$</TEX> 이였다. NADH:DCIP oxidoreductase의 활성은 <TEX>$Na^+$</TEX>또는 <TEX>$K^+$</TEX>에 의해 감소되었다. 그 최적 pH는 5.5 였다. NADH:DCIP oxidoreductase의 활성은 rotenone, capsaicin, <TEX>$AgNO_3$</TEX>와 같은 호흡저해제에는 매우 저항적 이 였지만, <TEX>$40{\mu}M$</TEX> HQNO (2-heptyl-4-hydroxyquinoline-N-oxide) 존재하에서는 약 40% 저해되었다. 이들 결과로 부터, Bacillus cereus KCTC 3674의 호기적 호흡쇄와 연계된 NADH oxidase계는 energy coupling site가 결여된 HQNO-sensitive NADH:DCIP oxidoreductase를 소유하고 있는 것으로 추정된다. Membranes prepared from Bacillus cereus KCTC 3674, grown aerobically on a complex medium, oxidized NADH exclusively, whereas deamino-NADH was little oxidized. The respiratory chain-linkedNADH oxidase system exhibited an apparent <TEX>$K_m$</TEX> value of about <TEX>$65\;{\mu}M$</TEX> for NADH. Interestingly, the activity of NADH:DCIP oxidoreductase on NADH oxidase system was decreased remarkably by <TEX>$Na^+$</TEX> or <TEX>$K^+$</TEX>, and its optimal pH was 5.5. The activity of NADH:DCIP oxidoreductase was very resistant to the respiratory chain inhibitors such as rotenone, capsaicin, and <TEX>$AgNO_3$</TEX>, whereas it was inhibited by about 40% with <TEX>$40{\mu}M$</TEX> 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO). From the results, we suggest the possibility that the aerobic respiratory chain-linked NADH oxidase system of B. cereus KCTC 3674 may possess the HQNO-sensitive NADH:DCIP oxidoreductase lacking an energy coupling site.