MILTON J. CORMIER 285 



the concemiations tested. FMN and FAD are slightly inhibitory at 

 10-^ M whereas arsenate does not inhibit. 



It has been shown, in the case of firefly luminescence, that inorganic 

 pyrophosphatase can adversely affect the steady-state linninescence 

 (12) . Likewise, inorganic pyrophosphate can either inhibit or stimu- 

 late luminescence, depending upon whether it is added prior to or after 

 ATP. These results have been explained in terms of a primary ATP- 

 dependent activation reaction that results in the formation of luciferyl 

 adenylate and pyrophosphate (14). As seen from Table 3, inor- 

 ganic pyrophosphate has little or no effect on Renilla luminescence. 

 This is true regardless of the order in which pyrophosphate is added. 

 Furthermore, the addition of inorganic pyrophosphatase (300-600 

 units) has no effect on luminescence of this system. These observa- 

 tions are in direct contrast to those made by McElroy et al. (12) on 

 firefly luminescence, and indicates a difference in the mechanism of 

 ATP action in the two systems. In addition, it would be difficult 

 to explain the stimulation of Renilla luminescence by AMP on the 

 basis of identical mechanisms. 



A requirement for free sulfhydryl groups in the luminescent sys- 

 tem is indicated by the inhibitory action of parachloromercviribenzoate 

 (PCMB) , N-ethylmaleimide, and copper and silver salts, as shown 

 in Table 3. The inhibition jjroduced by PCMB can be partially re- 

 versed (to 60% of the initial response) by the addition of 4 /xmoles 



TABLE 3 

 Effect of Inhibitors on Renilla Luminescence 



