182 



A SYMPOSIUM ON RESPIRATORY ENZYMES 



stable protein of muscle is added to the system, hexokinase is able 

 to transfer the labile phosphate group of adenosinediphosphate, the 

 reaction products in this case being adenylic acid and glucose-6- 

 phosphate. This is illustrated in Tables 4 and 5. 



Table 4.— Reaction of adenosinetriphosphate with glucose 



(Hexokinase and Mg++ in all samples. T = 30°C.) 



Time Po Pio Pio-Po 



Addition (min.) (7) (7) (7) 



Adenosinetriphosphate 4.0 68.0 64.0 



Adenosinetriphosphate 5 8.9 70.0 61.1 



Adenosinetriphosphate+glucose, 2 mg 5 8.8 43.8 35.0 



Adenosinetriphosphate 15 9.0 68.0 59.0 



Adenosinetriphosphate+glucose, 2 mg 15 9.5 43.4 33.9 



The diflFerence between the Pq and Pjo value (initial and ten-minute 

 hydrolysis values in normal sulfuric acid) corresponds to the amount 

 of labile phosphate added as adenosinetriphosphate. With a purified 

 hexokinase preparation of yeast, no appreciable reaction takes place 



Table 5.— Necessity of heat-stable muscle protein for reaction of 

 adenosinediphosphate with glucose 



(Hexokinase and Mg++ in all samples. Time, 5 minutes. T = 30°C.) 



Addition 



Pio— Po 



(7) 



AdenosineM'phosphate 51.8 



Adenosine/rzphosphate-l- glucose 28.4 



Adenosine<nphosphate-|-glucose-}-myokinase 7.6 



Adenosine<ftphosphate 62.4 



Adenosine^iphosphate+glucose 62.9 



Adenosinec/?phosphate-|-glucose-|-myokinase 16.0 



when adenosinetriphosphate alone is added; when glucose is also 

 added, approximately half of the labile phosphate of adenosinetri- 

 phosphate disappears. The reaction is a rapid one, since it is nearly 

 completed during five minutes of incubation at 30° C. Table 5 shows 

 the effect of a heat-stable protein of muscle which has been named 



