1961 年 81 巻 12 号 p. 1767-1774
It has been found that the resting cells obtained by stationary cultivation of Escherichia coli K-12 cultured in a liquid medium containing 1% each of peptone, bouillon, and glucose, reduce nicotinic acid N-oxide in the presence of a hydrogen donor like formate and glucose. Examinations of culture conditions revealed that cells obtained on shaking culture and cultured in a medium containing nitrate ion lacked the activity to reduce nicotinic acid N-oxide. The resting cells lacking this reducing activity, incubated with nicotinic acid hydrazide, in the presence of casamino acid and formate at 37°C, was found to regain the activity of reducing nicotinic acid N-oxide after about 1 hour.
Cells having reducing activity were treated with sonic waves in order to take out the reductase for nicotinic acid N-oxide in cell-free state. The supernatant obtained by centrifugation at 18000g for 30 minutes did not show any reduction of nicotinic acid N-oxide by itself but coupling of nitrate-adapted cells, lacking in the ability to reduce nicotinic acid N-oxide, with hydrogen transfer system resulted in marked reduction in the presence of methyl viologen. This fact suggests that, although the reductase is present in this supernatant, it lacks the hydrogen (or electron) transfer system and this system is regenerated by addition of nitrateadapted system, lacking in nicotinic acid N-oxide reductase, thereby resulting in the reduction of nicotinic acid N-oxide.