53 



Table 3-2. Prephenate aminotransferase amino acid donor 

 specificity in C. sorokiniana. 



L-Amino Acid Donor (10 mM) Specific Activity 



GLU leTo 



ASP 8 . 



TYR 2 . 



LEU 



ALA 



^A concentration of 1 mAf PPA was used in combination with 

 the amino acids. S. A. is nmol min" mg protein' 



When C sorokiniana extract was incubated at 65°C for 10 

 min and then assayed at 37°C, activity with PPY as keto acid 

 substrate was lost, but activity with PPA remained constant. 

 At 70°C for 20 min, however, about 60% of the PAT activity was 

 lost (Table 3-3) . 



Table 3-3. Prephenate aminotransferase activity after 

 thermal treatment in C. sorokiniana^. 



Aminotransferase 

 Couple 



No 

 treatment 



65"C 

 10 min 



70"C 

 10 min 



70"C 

 20 min 



PPA/GLU 

 PPY/GLU 



0.61 

 0.29 



0.60 

 



0.61 

 



0.25 

 



^Reaction mixtures were incubated at 37*C following thermal 

 treatment. Assays contained 1 mM PPA or 10 mM PPY, 10 mM GLU 

 and 0.05 mg protein. 



