structural requirements of substrates and inhibitors of guinea-pig brain guanine aminohydrolase ( gah ; e.c . 3.5.4.3 ) , have been established by working with guanine analogs ( 8-azaguanine , 1-methylguanine , thioguanine and guanosine ) , purine precursors ( 5-aminoimidazole-4-carboxamide ) , purinic bases ( xanthine , hypoxanthine , adenine and uric acid ) and pyrimidinic bases ( citosine , thymine and uracil ) .
C0040087
thymine
C0041917
uracil