passages.id: split_4_test_2071_passage
passages.type: progene_text
passages.text: The genes for dopamine synthetic enzymes , tyrosine hydroxylase ( TH ) , aromatic L-amino acid decarboxylase ( AADC ) , and GTP cyclohydrolase I ( GCH , an enzyme critical for tetrahydrobiopterin synthesis ) were contransduced into 293 cells with separate AAV vectors .