title: Functional analysis of pyrimidine 5'-nucleotidase mutants causing nonspherocytic hemolytic anemia.
abstract: Inherited pyrimidine 5'-nucleotidase type I (P5'N-1) deficiency is the third most common erythrocyte enzymopathy that causes hemolysis. Fourteen different mutations have been identified to date. We have investigated the molecular bases of the disease by studying the biochemical properties of the recombinant wild-type human enzyme and 4 variant proteins (D87V, L131P, N179S, and G230R) bearing missense mutations found in patients affected by nonspherocytic hemolytic anemia. P5'N-1 is a relatively stable protein and has essentially identical catalytic efficiency toward cytidine monophosphate (CMP) and uridine monophosphate (UMP). All investigated mutant proteins display impaired catalytic properties and/or reduced thermostability, providing a rationale for the pathological effects of the mutations. Despite the substantial changes in the kinetic and thermostability parameters, the enzyme activity detected in the red blood cells of patients homozygous for mutations L131P and G230R exhibits moderate alterations. This suggests that P5'N-1 deficiency is compensated, possibly by other nucleotidases or alternative pathways in nucleotide metabolism. Therefore, nucleotidase activity may not be considered a prognostic indicator in patients affected by the enzymopathy.
authors.affiliation: Department of Biochemistry, University of Pavia, Pavia, Italy.
authors.forename: Laurent R
authors.initials: LR
authors.lastname: Chiarelli
authors.forename: Paola
authors.initials: P
authors.lastname: Bianchi
authors.forename: Elisa
authors.initials: E
authors.lastname: Fermo
authors.forename: Alessandro
authors.initials: A
authors.lastname: Galizzi
authors.forename: Paolo
authors.initials: P
authors.lastname: Iadarola
authors.forename: Andrea
authors.initials: A
authors.lastname: Mattevi
authors.forename: Alberto
authors.initials: A
authors.lastname: Zanella
authors.forename: Giovanna
authors.initials: G
authors.lastname: Valentini
mesh_terms: D015720:5'-Nucleotidase / Q000235:genetics* / Q000378:metabolism*; D000743:Anemia, Hemolytic / Q000235:genetics* / Q000378:metabolism*; D002384:Catalysis; D004789:Enzyme Activation; D005838:Genotype; D006358:Hot Temperature; D006801:Humans; D020125:Mutation, Missense; D010641:Phenotype
chemical_list: D015720:5'-Nucleotidase