392 Photosynthesis 



Suspension, the expelled CO> will for the most part be taken iip again. The energy 

 of the respiration induced by the added O2 is necessary for this rebinding of COo. 

 Obviously, the analogy here to the dark reaction in photosynthesis is very far- 

 reaching. 



Second, and equally important : if one expels the labile CO> from the Chlorella 

 with low concentrations of fluoride, and then illuminates, photosynthesis is found 

 to be inhibited; but if one removes the fluoride from the cells by washing, and 



Fig. 7. 



Vessel for measuring labile COj 



Suspension 

 of Chlorella 



waits until the CO2 is again aerobically bound, the photosynthetic capacity is 

 found to be restored. Labile CO2 and photosynthesis are thus mutually depen- 

 dent. 



We have spared no pains to discover what the chemical source of the labile CO 2 

 is. We have found that it is L-glutamic acid 8 , which occurs in Chlorella in loosely 

 bound form to the extent of 0.5 to 1 percent of the dry weight. This glutamic acid 

 goes into the external medium when a Chlorella Suspension is heated at 90° C for 

 several minutes. If one determines the glutamic acid content of the centrifuged 

 external medium before and after a treatment with fluoride, one finds that as much 

 glutamic acid has disappeared as CO2 has been developed by the fluoride ! 



7-Aminobutyric acid is formed along with the CO2 in the fluoride reaction. 

 Aerobically, y-aminobutyric acid and CO2 react in the cells to yield glutamic acid 

 again, so that aerobically a stationary State is set up between decomposition and 

 resynthesis of glutamic acid : 



L-Glutamic acid ^z ;'-aminobutyric acid - ; COo 



The '/.-decarboxylation of glutamic acid was discovered in bacteria in 1910 by 

 Ackermann and in green plant cells in 1937 by the Japanese Okonuki. Both the 



