Residual Purine Nucleoside Phosphorylase-Activity In A New Dutch Patient With Pnp-Deficiency And Cellular Immunodeficiency

A deficiency of purine nucleoside phosphorylase (PNP) was detected in a three-year-old boy who was admitted for the investigation of behaviour disorders and spastic diplegia. The urinary excretion profile of oxypurines, analyzed by liquid chromatography, showed the presence of large amounts of (deoxy)inosine and (deoxy)guanosine together with a low uric acid. The PNP activity in red blood cells and peripheral blood lymphocytes was not detectable by standard methods. However partial purification of the red cell enzyme demonstrated some residual PNP activity equivalent to 0.5% of a control haemolysate. This residual activity enabled the characterization of the enzyme. Immune precipitation studies with anti-PNP antiserum (gift of Dr. W.R.A. Osborne, Seattle) showed that the amount of the residual protein was approximately 0.5% of the control value as well. The other enzyme properties studied including substrate affinity (inosine), substrate specificity, electrophoretic mobility and heat stability, were all completely normal. Erythrocyte PNP activities in both parents were in the heterozygote range (35 and 50%) and the enzyme properties were normal as well.