7 biopterin

7-Biopterin is a 7-substituted pterin.1It is formed by non-enzymatic rearrangement of 4a-hydroxy-tetrahydropterin in the absence of pterin-4a-carbinolamine dehydratase (PCD)in vitroand levels are elevated in the urine of hyperphenylalaninemia patients carrying heterozygous mutations in the PCBD gene encoding PCD.1,2