188 



METABOLISM AND PHYSIOLOGY 



TABLE 8 



NoncycUc PJwtopliosphorylatioii 



Additions 



//moles ATP formed/mg 

 Bchl/hr 



All vessels contained 10 /ug antimycin A. The final concentrations of the 

 added components were: ascorbate, 6.7 x 10"*^ M; 2,6-dichlorophenol indophenol 

 (DPIP), 6.7 X 10-5 M; DPN, 6.7 x 10-4 M; and phenyl mercuric acetate (PMA), 

 10-4 M. Other conditions and components of the phosphorylating mixture were 

 the same as given in Table 1. 



greater than one, suggesting that the chromatophores might have con- 

 tained a DPNH2 reoxidizing system. 



DPN dependence 



Since the concept of noncyclic photophosphorylation (22) envisages 

 that the ATP formed by this pathway is obligatorily coupled with an 

 electron flow from the ascorbate-DPIP couple to DPN, ATP formation 



TABLE 9 

 StoicliioDietry of ATP and DPNHp Formed in Noncyclic Photophosphorylation 



In the presence of DPNH 

 trapping system 



In the absence of DPNH 

 trapping system 



The reaction mixture included, in a final volume of 3 ml, chromatophores 

 containing 40//gof bacteriochlorophyll, and the following in //moles: tris buffer, 

 pH 7.8,100; MgCl2, 5; ADP, 5; K2HP32O4, 5; ascorbate, 20; 2-6 dichlorophenol 

 indophenol, 0.2; DPN, 5. Where the DPN trapping system was used, DPN was 

 reduced to 0.2 //moles, and 10 //moles of pyruvate and 25 //g of lactate dehydro- 

 genase were added. All vessels contained 10 //g of antimycin A. The reaction 

 was run in Thunberg type cuvettes at 20°C in the light (10,000 lux). 



