60 

 present in Chlorella for DQT and/or SDH, (ii) some component 

 in crude extract inhibits the SDH activity or (iii) DHS, the 

 product of the reaction is being utilized by another 

 protein. The second possibility may also apply to ADT and 

 ADH since activity was not found in crude extracts but was 

 located in column fractions. 



Most interesting, is the similarity of PAT in Chlorella 

 to that of higher plants, each having the high optimal 

 temperature for activity. At 65°C, the aminotransferase (s) 

 using the PPY/GLU couple was inactivated. The high 

 specificity of Chlorella for the substrate couple of PPA and 

 GLU was also consistent with higher plant PAT (5, 6) . From 

 these data, it is suggested that C. sorokiniana has an 

 aromatic biosynthetic pathway similar to that established 

 for higher plant chloroplasts. Supportive evidence would 

 include the isolation of Chlorella chloroplasts to determine 

 the location of the aromatic pathway enzymes. The isolation 

 and sequencing of cDNA clones coding for S -protein, PAT and 

 ADH (see Chapter VI) may be useful as probes to clone the 

 appropriate genes in Chlorella. 



Arogenate dehydratase activities paralleled a similar 

 experiment with respect to the chloroplast isoenzyme of DAHP 

 synthase (Ds-Mn) , where growth of cells and enzyme 

 activities where followed (32) . Both enzymes rise in 

 exponential growth and decline in stationary phase of 

 growth. ADT exhibited an opposite pattern of activity to 



