Applications 2,4-Diamino-6-hydroxypyrimidine is a selective inhibitor of GCH-I (GTP cyclohydrolase I). Suppression of this enzyme by 2,4-Diamino-6-hydroxypyrimidine impedes tetrahydrobiopterin biosynthesis and abolishes both lipopolysaccharide-induced elevation of biopterin levels and lipopolysaccharide-induced NO synthesis. Description 2,4-Diamino-6-hydroxypyrimidine is a selective inhibitor of GCH-I (GTP cyclohydrolase I). Suppression of this enzyme by 2,4-Diamino-6-hydroxypyrimidine impedes tetrahydrobiopterin biosynthesis and abolishes both lipopolysaccharide-induced elevation of biopterin levels…