64 



E. C. Slater and W. C. Hulsmann 



10 15 20 

 Time (min.) 



25 30 35 



Fig. 3. Respiratory control with rat 

 heart sarcosomes, isolated as in Fig. 2 

 and studied in the same reaction mixture. 

 Curve 1, no further addition. Curve 2, 

 0-02 M glucose + hexokinase (P/O ratio 

 measured on this flask = 2-13); curve 3, 

 10-4 M DNP; curve 4, 0-0033 m ADP. 

 (From Holton et al., 1957. Reproduced by 

 permission of the Editors, Biochem. J.) 



occur before the introduction of phosphate into the 

 reaction scheme, i.e. it must involve A '^' I, or X '-^ I, 

 rather than X ^^ P. Since A ^^ I is excluded by the 

 considerations just mentioned, it is concluded that 

 DNP promotes the hydrolysis of X ^^ I. 



The DNP-stimulated ATPase reaction is explained by the 

 reaction sequence: 



ATP + X ^=:± X ^ P + ADP (4) 



X -^ P + I ^==i X ^ I + Pi (5) 



X ^ I + HgO 



(DNP) 



x + i 



(6) 



Sum reaction ATP + ILfl 



(DNP) 



> ADP + Pi 



