Primapterin (7-iso-biopterin) is a new pterin metabolite found recently in the urine of a child with mild hyperphenylalaninaemia . Besides primapterin two other new 7-substituted pterins, namely 6-oxo-primapterin and anapterin (7-iso-neopterin), were also found in the patient's urine, however in much lower concentrations (Curtius et al., 1988). In the meantime a second patient has been diagnosed with primapterinuria and transient hyperphenylalaninaemia (Blaskovics, personal communication). In both cases a tetrahydrobiopterin (BH4) loading test normalized plasma phenylalanine levels after 4 to 6 h. In both patients the cerebrospinal fluid (CSF) neurotransmitter metabolites, 5-hydroxyindoleacetic acid and homovanillic acid were in the normal range and the activities of all enzymes of the BH4 biosynthesis and regeneration (GTP cyclohydrolase I, 6pyruvoyltetrahydropterin synthase, sepiapterin reductase and dihydropteridine reduct as e) were found to be normal. The neopterin to biopterin ratio of the patients' urine was significantly increased. Following oral tetrahydrobiopterin administration (2 mg kg-1d-1 ) neopterin normalized and biopterin as well as primapterin increased about eight-fold in one of the patients. This finding suggests that primapterin is formed from biopterin by an isomerization reaction. However, the exact metabolic origin of primapterin and anapterin is still obscure. MATERIALS AND METHODSPteridin standards were purchased from Dr B. Schircks Lab. (Jona, Switzerland), 7-iso-neopterin and 7-iso-biopterin were a gift from Professor H. Rembold, Munich, FRG. The respective tetrahydro compounds were prepared by catalytic hydrogenation with Pd/H 2 • HPLC of pterins after oxidation with manganese dioxide was

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This report concerns a patient with severe congenital lacticacidosis associated with proximal renal tubular acidosis and cystinuria. Enzyme studies with cultured skin fibroblasts obtained from the patient revealed zero pyruvate carboxylase activity, but propionyl-CoA carboxylase activity was normal. Administration of various vitamins in large amounts did not improve the clinical condition. In contrast, the patient began to thrive when her diet was supplemented with aspartic acid, asparagine, glutamic acid, and glutamine. The particular dietary treatment used and the biochemical findings merit consideration for management of future cases.

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