TRYPTOPHAN METABOLISM 



323 



unstudied reactions are likewise inhibited. A more indirect mechanism is 

 the inhibition of the synthesis of tryptophan synthetase in growing cells, 

 whereby tryptophan formation is further reduced. 



100 



Fio. 2-6. The inhibition of E. coli growth by 4-methyltryptophan 

 at 0.01 mM and its antagonism by increasing tryptophan con- 

 centrations. (From Trudinger and Cohen, 1956.) 



Tryptophanase 



This bacterial and fungal enzyme may be involved in the fermentation 

 of tryptophan and is responsible for the putrefactive reaction in the in- 

 testines. It is potently and competitively inhibited by the product indole 

 and less potently by some analogs (as shown in the accompanying tabula- 



Inhibitor 



Relative — AF of binding 

 (kcal/mole) 



Indole 



/?-3-Indolylpropionate 



3-Indolylacetate 



/?-3-Indolylethylamine 



DL-/3-l-Methyl-3-indolylalanine 



5.40 

 4.05 

 3.76 

 2.55 

 1.44 



