394 



F. EgAMT, M. ISHIMOTO AND S. TaNIGUCHI 



The anaerobic cells cultured anaerobically with nitrate and containing the 

 active mechanism of nitrate respiration were used throughout this study. 



The nitrate reductase activity was found in the particulate fraction 

 (sedimented at 2,000-20,000^) with cytochrome b^ and formate dehydro- 

 genase after alumina or sonic destruction of cells (Table 2). This particulate 



Table 2. Distribution of nitrate reductase, formate dehydrogenase 



AND PROTOHAEM IN CELLULAR FRACTIONS OF E. CoU 



40 g of wet cell paste was ground with alumina and subjected to the foUowing centrifugal fractionation. 

 All determinations at 30°C. 



* The donor for NaR was MVH. One unit of NaR is defined as an amount of the 

 enzyme which produces 1 /<mole of nitrite in 1 hr. Specific activity is defined as units/mg N. 



t Acceptor for FDH was Mb. Activity is expressed as the amount of enzyme which 

 reduces 1 /<mole of Mb in 1 hr. 



Table 3. Comparison of electron donors for 

 particulate nitrate reductase activity 



X Electron donors except formate and DPNH were 

 reduced by dithionite. All compounds at 2 x 10^ m con- 

 centration except reduced FAD and reduced FMN (both 

 at 2 X 10 » m) and formate (5 x 10"' m). 



