8578
Further studies indicated that inhibition of GTP-cyclohydrolase I (an enzyme involved in de novo synthesis of an important cofactor for NOS activity , tetrahydrobiopterin) prevented the generation of NO in A/R -tolerant cells .
 ( protein: NOS, None) , ( cell line: A/R -tolerant cells, None) , ( protein: GTP-cyclohydrolase I, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: NOS, None) , ( cell line: A/R -tolerant cells, None) , ( protein: GTP-cyclohydrolase I, None) 