THE CHEMIS'IRY OF PHOTOSYNTHESIS 163 



§ 61 Amino-acids in Chlorella 



Warburg et al. (10, 11) found that Chlorella contains a very active glutamic 

 acid decarboxylase which anaerobically splits glutamic acid into 7-amino- 

 butyric acid and CO2. Under aerobic conditions the reaction proceeds in 

 the opposite direction. 



anaerobic 

 rnOR ■ r^H, • THo • r.HNHo • rooH -, > nooH • CH, • P.H, • nHoNH, + CO2 



glutamic acid aerobic y-amitwbutyric acid 



With respect to HCN, this reaction behaves like the fluoride reaction, so that 

 it was supposed that the latter is nothing but decarboxylation of glutamic 

 acid. It has indeed been established that the COo removed by NaF origi- 

 nates fiom glutamic acid. It has been possible to show by means of paper 

 chromatography that during the fluoride reaction glutamic acid disappears 

 and 7-aminobutyric acid is produced. Chlorella cultivated under special 

 conditions is able to develop CO2 anaerobically without the addition of NaF 

 (see § 62). Paper chromatography with aspartic acid, glutamic acid, ala- 

 nine and 7-aminobutyric acid as test substances showed, according to War- 

 burg (6), that Chlorella under its normal living conditions contains little 

 aspartic acid, much glutamic acid, very much alanine but no 7-aminobutyric 

 acid. 



Warburg et al. (6, 12) used labeled CO2 to study the behavior of glutamic 

 acid in photosynthesis. A manometer vessel contains a Chlorella suspension. 

 The side-arm of the vessel is divided into two compartments, one containing 

 ^^C^arbonate and the other an excess of lactic acid. When the lactic acid 

 is given to the carbonate, a pressure of radioactive CO2 develops in the ves- 

 sel. The vessels prepared in this way are illuminated for 0.5, 1 and 5 min. 

 Afterwards, they are, together with control vessels kept in the dark, immersed 

 for 5 min in water at 75 ° C to stop enzymatic reactions and, at the same time, 

 to extract the soluble substances from the cells. The extracts obtained are 

 analyzed by two-dimensional paper chromatography and the activities of the 

 spots measured with a Geiger counter. It follows from these experiments that 

 amino-acids become radioactive much more rapidly than 3-phosphoglyceric 

 acid, which was generally thought to have priority in similar investigations. 

 Furthermore, it was found that aspartic acid and alanine became radioactive 

 more quickly than glutamic acid. From this it may be concluded that a chain 

 of amino-acids acts as a catalyst in Chlorella. In this peptide chain glutamic 

 acid does not seem to occupy the first place. 



In his investigations on chloroplastin, Kaufmann (1) observed that the 

 grana proteins of various higher plants contain a series of loosely bound amino- 

 acids, glutamic acid being quantitatively predominant. The grana were 

 washed by the method of Warburg and Liittgens (3) to remove the greater 

 part of the glutamic acid. Thus, living chlorophyll must be considered to be 



