FU^XTION OF FLAVOENZYMES IX ELECTRON TRANSPORT 



141 



concerning the cellular function of DT diaphorase. This may enable us 

 now to examine critically the role of vitamin K reductase, which, as is well 

 known, has been postulated by Martins [3, 4] to constitute the exclusive 

 pathway of reduced pvridine nucleotide oxidation, and of oxidative 

 phosphorylation, in normal, intact mitochondria. The experimental data 

 to be presented have been obtained in collaboration with Dr. T. E. Conover 

 and Air. L. Danielson. 



TABLE I 

 Comparison of Vitamin K Reductase and DT Diaphorase 



Vitamin K Reductase 

 (Martius et ol., 1954-S9 



[1-4]) 



DT Diaphorase 



(P^rnster et al., i960 



[15]) 



\"itamin K Reductase 

 (Miirki and Martius, i960 



[21]) 



Flavoenzyme 

 (turnover number, 

 I -2 X 10"). 



Reacts with DPXH and 

 TPNH at equal rates. 



Reacts specifically with 

 vitamin Kj 



Strongly inhibited by 

 dicoumarol. 



Inhibited bv thvroxine. 



Not inhibited by p- 

 chloromercuribenzoate. 



Present in mito- 

 chondria. 



Flavoenzyme 



(turnover number, 

 - lo'). 



Reacts with DPXH and 

 TPXH at ecjual rates, but 

 affinitv slightlv higher for 

 TPXH. 



Reacts with dyestuffs, 

 ferricyanide, various 

 naphtho- and benzo- 

 quinones, but not with 

 vitamin Ki and other 

 long-chain substituted 

 quinones. 



Strongly inhibited by 

 dicoumarol. 



Inhibited by thyroxine 

 (and related compounds). 



Inhibited by /)-chloro- 

 mercuribenzoate. 



Activated by bovine 

 serum albumin. 



Present in mitochondria 

 and microsomes, but bulk 

 m soluble cytoplasm. 



Flavoenz\Tne 

 (turnover number, 



7 X lO^). 



Reacts with DPXH and 

 TPX'H at equal rates, but 

 affinitv slightlv higher for 

 TPXH. 



Reacts with dyestuffs, 

 ferricyanide, various 

 naphtho- and benzo- 

 quinones, but not with 

 vitamin Kj and other 

 long-chain substituted 

 quinones. 



Strongly inhibited by 

 dicoumarol. 



Xot inhibited by 

 thyroxine. 



Xot inhibited by /)- 

 chloromercuribenzoate. 



.Activated by bovine 

 serum albumin. 



Present in mitochondria, 

 but bulk in soluble 

 cytoplasm. 



REL.\TION TO MITOCHONDRIAL RESPIRATORY CHAIN 



When intact rat liver mitochondria were incubated with glutamate, and 

 under conditions allowing optimal rates of respiration and phosphorylation, 

 addition of 5 x 10 "^ m vitamin K3 or lO"'' m dicoumarol had no effect on 

 the rate of oxygen consumption (Table II). However, when respiration 



