Liver enzyme activities in hyperphenylalaninaemia due to a defective synthesis of tetrahydrobiopterin

This report confirms the accumulation of neopterin and the low biopterin concentration in the liver of a "biopterin-synthetase" deficient patient. Enzymatic studies suggest that the defect lies between the "X"-compound (6-pyruvoyl-tetrahydropterin?) and tetrahydrobiopterin and that pterin found in the patient's liver arises from the "X"-compound.