THE CHEMISTRY OF PHOTOSYNTHESIS 173 



In X-cells containing 5 times as much glutamic acid as chlorophyll War- 

 burg found that 100 fx\ cells contained 1.9 /xiTiole glutamic acid and 0.418 

 fxmole chlorophyll and that the saturation value for aerobically dissociating 

 CO2 was 1.9 ^tmole. Thus, in these cells, too, the saturation value for aerobi- 

 cally dissociating CO2 is equal to the glutamic acid content, but not to that of 

 the chlorophyll content. 



To summarize these most interesting findings, Chlorella contains three types 

 of COo: 



1 . COo^ of glutamic acid which is not dependent on CO2 pressure. 



2. COo , originating from bicarbonates, which is dependent on COo pres- 

 sure. 



3. COo , i.e., the dissociating COo, originating in the presence of Oo, 

 which is dependent on the COo pressure and occurs in a concentration of 

 the same magnitude as that of glutamic acid. 



It is possible to establish the three COo values by means of the fluoride method 



(5): 



saturation of the cells with argon : .y ^ul CO2 



saturation of the cells with argon + 1 vol % COo : y ix\ COo 



saturation of the cells with argon + 10 vol % COo + Oo: z m1 CO2 



We then have 



COo' = .V m1 



COo" = (v - .v) Ml 



CO,'" = u -V) Ml 



In the light glutamic acid does not decrease, but aerobically dissociating 

 COo decreases markedly. After 5 min illumination at high intensity (800 

 ix\ quanta/min) the aerobically dissociating COo decreased in one experiment 

 (100 n\ A-cells) from 77 /xl to 49 /xl. When the cells were put in the dark 

 afterwards ^/so A^ NaF developed 75 m1 CO2 after 20 min. Thus, the light 

 value (49 ^1) increased within 20 min in the dark to its initial value. On illu- 

 mination the O2 capacity of cells which were previously in the dark sets in, 

 and the dissociating COo decreases markedly during the stoichiometric O2 

 production. However, in the dark, when induced respiration restores Oo 

 capacity, the dissociating CO2 increases to its initial value (12). 



§ 66 The Carotenoid Oxygenase of Chlorella 



When a small amount of octanol or quinone is added to Chlorella (south cells 

 suspended in salt solution K or S) in the dark, respiration ceases. Neverthe- 

 less, there is a very pronounced Oo uptake without production of COo. The 

 O2 consumption of 200 ^1 cells at 20° C and at pH 6.5 is about 500 jA per 

 hour, i.e., 5 times greater than the Oo uptake during respiration. Warburg 

 et al. (20), who discovered this reaction, showed that lyophilized cells oi Chlo- 

 rella — without addition of quinone — behave in the same way. Brief heating 

 to 65 ° C stops the reaction, which is therefore assumed to be of an enzymatic 



