On the other hand, 6-amino-8-hydroxypurine is detected in urine of patients with adenine phosphoribosyltransferase (APRT) deficiency; this finding indicates that hydroxylation of adenine occurs at the 8-position prior to the 2-position, though the reaction is extremely slow [27]. This evidence concerns the gene APRT and hyperinsulinemic hypoglycemia, familial, 4.