title: Identification of mucopolysaccharidosis I heterozygotes based on biochemical characteristics of L-iduronidase from dried blood spots.
abstract: BACKGROUND
  Mucopolysaccharidosis I (MPS I) is a genetic disorder caused by deficiency of L-iduronidase (IDUA) activity. Heterozygote screening is a highly requested service by risk families; however, determination of IDUA activity alone is not sufficient to discriminate between heterozygotes and normal individuals because a significant overlap occurs between them. The aim of this study was to characterize the enzyme eluted from heterozygote's dried blood samples and determine if there are differences with that of normal individuals.
  
  
  METHODS
  We determined Km, Vmax and the thermal stability of the enzyme at 50 °C.
  
  
  RESULTS
  Vmax from heterozygotes (7.28 ± 2.72 μmol/l blood/h) was significantly different than the obtained in controls (10.52 ± 2.05 μmol/l blood/h), while their Km were similar: 0.633 ± 0.339 mmol/l and 0.672 ± 0.246 mmol/l, respectively. After a 12 h pre-incubation period, IDUA activity in controls was significantly lower compared to heterozygotes.
  
  
  CONCLUSIONS
  IDUA eluted from dried blood spots of heterozygotes differs from that of controls in terms of Vmax and thermal stability. These parameters can be used as an important tool for the detection of carriers for MPS I. This is the first report describing a differential behavior of these parameters for a lysosomal enzyme obtained from dried blood.
authors.affiliation: Department of Biochemical Genetics, National Center of Medical Genetics, 146 Street No. 3102, Havana, Cuba. Electronic address: derbisch81@gmail.com.
authors.forename: Derbis
authors.initials: D
authors.lastname: Campos
authors.affiliation: Department of Biochemical Genetics, National Center of Medical Genetics, 146 Street No. 3102, Havana, Cuba.
authors.forename: Madelyn
authors.initials: M
authors.lastname: Monaga
authors.affiliation: Neonatal Research Laboratory, Center of Immunoassays, 134 Street and 25 Ave, Havana, Cuba.
authors.forename: Ernesto C
authors.initials: EC
authors.lastname: González
authors.affiliation: Department of Biochemical Genetics, National Center of Medical Genetics, 146 Street No. 3102, Havana, Cuba.
authors.forename: Darlenis
authors.initials: D
authors.lastname: Herrera
mesh_terms: D017920:Antiporters; D059788:Dried Blood Spot Testing; D004795:Enzyme Stability; D006580:Genetic Carrier Screening; D006801:Humans; D007068:Iduronidase / Q000097:blood / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008059:Mucopolysaccharidosis I / Q000175:diagnosis / Q000201:enzymology* / Q000235:genetics*; D013696:Temperature
chemical_list: D017920:Antiporters; C045885:sodium-lithium countertransporter; D007068:Iduronidase
keywords: Dried blood spots; IDUA; Lysosomal storage diseases; MPS I; Mucopolysaccharidosis I heterozygotes