Purine nucleoside phosphorylase deficiency: altered kinetic properties of a mutant enzyme

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Science  09 Sep 1977:
Vol. 197, Issue 4308, pp. 1084-1086
DOI: 10.1126/science.407651


Erythrocyte purine nucleoside phosphorylase from two brothers had 0.5% of normal activity. It differed from the normal enzyme by a tenfold increase in the Michaelis constant for inosine, an inability of inosine to protect against thermal lability, and a more positive net charge. The altered kinetic properties may account for the milder disease in the patients compared to the previously described cases. The data provide evidence for a structural gene mutation and genetic heterogeneity in the new disease of purine nucleoside phosphorylase deficiency and T cell dysfunction.