title: Purine nucleoside phosphorylase deficiency: altered kinetic properties of a mutant enzyme.
abstract: 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.
mesh_terms: D002648:Child; D004912:Erythrocytes / Q000201:enzymology; D006801:Humans; D007042:Hypoxanthines / Q000378:metabolism; D007154:Immune System Diseases / Q000201:enzymology / Q000235:genetics; D066298:In Vitro Techniques; D007288:Inosine / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009154:Mutation; D010430:Pentosyltransferases / Q000172:deficiency*; D011683:Purine-Nucleoside Phosphorylase / Q000097:blood / Q000172:deficiency* / Q000378:metabolism
chemical_list: D007042:Hypoxanthines; D007288:Inosine; D010430:Pentosyltransferases; D011683:Purine-Nucleoside Phosphorylase