FUNCTION OF FLAVOENZYMES IN ELECTRON TRANSPORT 1 63 



TABLE XIII 



Insensitivitv of Succinate-linked Reduction of Acetoacetate to 



axtimycin a 



(Azzone, Ernster, and Weinbach, unpublished) 



In each flask: mitochondria from 300 mg. liver, 50 m.M KCl, 20 m.M glycyl- 

 glycine, pH 7-5, 12-5 mM Pj, 8 mM MgCL, 10 mM succinate, 3 mM acetoacetate, 

 and, where indicated, 20 mM ferricyanide, i /xg./ml. antimycin A and 0-5 niM 

 KCN. Final volume, 2 ml. Incubation at 30" for 20 min. 



Additions /tmoles AcAc reduced 



None 2-6 



KCN 0-3 



KCN + (Fe(CN)6)'+ 2-0 



KCN + (Fe(CN)6)'+ + Antimycin A 2-4 



reduction of acetoacetate was completely insensitive to antimycin A 

 (Table XIII). 



AMINATIVE REDUCTION OF a-KETOGLUTARATE BY SUCCINATE 



Before terminating my report, let me briefly show you some pre- 

 liminary data obtained with another dehydrogenase, glutamic dehydro- 

 genase, as a trapping system for the DPNH generated by succinate-linked 

 DPN-reduction. This system was very similar to that used by Hunter and 

 Hixon in 1949 [51] for the demonstration of a-ketoglutarate-linked sub- 

 strate-level phosphorylation. It consisted of liver mitochondria incubated 

 under anaerobic conditions in the presence of x-ketoglutarate and am- 

 monia. In this system, as Hunter and Hixon ha\e shown, the following 

 reaction takes place : 



2a-ketoglutarate -h NH3 + ADP + P, > 



glutamate + succinate + COo + ATP (5) 



However, unlike Hunter and Hixon 's system, the present one was not 

 supplemented with a terminal phosphate acceptor. It was thus expected 

 that the ATP and succinate formed in the a-ketoglutarate oxidation would 

 give rise to a reduction of DPN, after which the DPNH so generated would 

 reduce another molecule of o^-ketoglutarate ( + ammonia) to glutamate. 

 This reaction sequence may be written as follows : 



succinate + ATP + DPN ^=i fumarate + ADP + P, + DPNH (6) 



DPNH + a-ketoglutarate + NH3 t " DPN + glutamate (7) 



The net reaction of Reactions 57 is : 



3a-ketoglutarate -I- 2NH3 > 2 glutamate + fumarate + CO2. 



