234 



Van R. Potter and Hermann Niemeyer 



Aisenberg and Potter, 1957; Gatt, Krimsky and Racker, 

 1956; Tiedemann and Born, 1958). The action of fresh mito- 

 chondria is very complex, because they contribute many 

 enzyme systems that may interfere with glycolysis through 

 different mechanisms (Aisenberg and Potter, 1957). In 

 addition to their capacity to oxidize the pyridine coenzymes 



A GLUCOSE ' +A LACTATE '- A ORTHOPHOS- 



ooCONTROL ^-•+TPN PHATE 



^8 72 7.6 8.06.8 72 7.6 8.0 6.8 7.2 7.6 8.0 

 pH 



Fig. 1. Influence of pH on glycolysis and on the effect of 

 TPN. Each flask contained in a 1 • 6-ml. volume, • 5 ml. 

 brain-Sg, 7-5 [im glucose, 2 y.M ATP, 1 [im DPN, 60 [lm 

 nicotinamide, 6 (jiM-MgCla, 15 [xm potassium phosphate at the 

 required pH ; potassium bicarbonate in concentration to give 

 the required pH when equilibrated with 95 per cent O2-5 per 

 cent CO2, 3 [jlm TPN when indicated. • 15 m-KCI to maintain 

 isotonicity. 



and pyruvate and to carry out oxidative phosphorylation, 

 they contain variable amounts of coenzymes and may be often 

 contaminated in the case of the liver with G-6-Pase from the 

 microsome fraction, which obscures the interpretation of some 

 experimental data. For these reasons, aged liver mitochondria 

 were preferred for further studies. They are depleted of 

 coenzymes (Siekevitz and Potter, 1955), but are able to oxidize 

 DPNH through the DPN-cytochrome c reductase and TPNH 

 through transhydrogenase and the preceding enzyme (Reina- 

 farje and Potter, 1957). On the other hand, they are presum- 



