278 



LIGHT AND LIFE 



At this point it is significant to note that crude extracts contain 

 a phosphatase (s) that causes the Hberation of inorganic phosphate 

 from ATP and ADP. In one experiment, for example, it was found 

 that a preparation containing 1.5 mg protein/ml caused the release 

 of 0.5 and 1.0 ^mole of Pj per 10 minutes from ADP and ATP, re- 

 spectively, under the experimental conditions used. Under condi- 

 tions that support luminescence, then, these extracts apparently con- 

 vert ATP to ADP, whereas ADP is apparently converted to AMP. 

 That these products are actually formed via phosphatase action was 

 confirmed by separation and identification of the nucleotides on 

 formate-charged Dowex-1 columns, as described by Hurlbert et al. 

 (9) . The fact that ATP can be broken down to ADP and AMP in 

 the crude extracts, whereas AMP or ADP are not converted to ATP, 

 suggests that ATP functions as a generating system for ADP and 

 AMP and that one (or both) of the two latter nucleotides is directly 

 responsible for driving the light reaction. This suggestion is now 

 known to be the correct interpretation, and the supporting data are 

 given later. 



The effect of nucleotide concentration on the luminescence of 

 Renilla extracts is illustrated in Fig. 1. The data plotted in Fig. 1 

 show that ATP is more effective than ADP or AMP at the lower con- 



14001 



1200 



1000 



200 



0.5 



NUCLEOTIDE CONCENTRATION (/imol.s/ml) 



Fig. 1. Effect of nucleotide concentration on the luminescence of Renilla 



renifnrmis extracts. 



