505 



Anthony San Pietro, Leo P. Vernon and Dorothy Limbach 



pmoles of NADP and the indicated additions in a final volume of 8 ml. 

 time of illumination was 5 minutes. 



The 



RESULTS 



The relationship between the rate of NADP photoreduction and the con- 

 centration of partially purified PPNR is shown in Fig. 1. At low protein con- 

 centration, there is a linear relationship between the rate of photoreduction 

 of NADP and protein concentration; at higher protein concentrations, the 

 rate is independent of protein concentration. This is not unreasonable since 

 the experiments were not carried out at saturating light intensity. In separ- 

 ate experiments it was established that the rate of photoreduction of NADP 

 was dependent on NADP concentration. 



92 1.83 366 5.49 7.32 



Mg PROTEIN (PPNR, Crude ) 



EXP. DLIOIA 



O 



< 



+ .4 - 



+.2 



-.2 



.035 .07 .105 .14 

 Mg. PROTEIN (PPNR) 



EXP. OL 102,106 



Fig. I. (Left) Effect of Partially Purified PPNR upon NADP 

 Reduction with Hematoporphyrin and Ascorbate. 

 Fig. 2. (Right) Lack of Effect of PPNR upon NADP Reduction 

 with Hematoporphyrin and Ascorbate. 



Contrary to the results obtained with the partially purified PPNR, the 

 purified PPNR was completely inactive in catalyzing the photoreduction of 

 NADP or NAD in this system (Fig. 2, Lower Curve). As can be seen there 

 is a photobleaching of the hematoporphyrin in the presence or absence of 

 purified PPNR (Fig. 2, Lower Curve). When transhydrogenase is included 

 in the reaction mixture, there is observed a photoreduction of NADP (Fig. 2, 

 Upper Curve). Furthermore, the rate of photoreduction of NADP in the 

 presence of transhydrogenase is unaffected by the presence or absence of 

 purified PPNR (Fig. 2, Upper Curve). 



The relationship between the rate of photoreduction of NADP and the con- 

 centration of transhydrogenase is shown in Fig. 3. It is seen that there is a 



