title: Improving arylsulfatase activity determination in dried blood spots: Screening and diagnostic approaches for Maroteaux-Lamy syndrome (MPS VI).
abstract: BACKGROUND
  Mucopolysaccharidosis type VI can be screened by measuring the lysosomal arylsulfatase B (ARSB) residual enzyme activity in dried blood spots (DBS) using synthetic substrates. However, we have found experimental obstacles when determining ARSB activity with the fluorescent method due to the significant quenching effect rendered by DBS components.
  
  
  METHODS
  We adapted the methods originally described by Chamoles et al. [1] and Civallero et al. [2] and put forward 2 distinct approaches for ARSB activity quantification from DBS samples by measuring the 4-methylumbelliferone (β-MU) fluorescence generated from the ARSB 4-methylumbelliferone sulfate (β-MUS) substrate.
  
  
  RESULTS
  We demonstrate the high throughput feasibility of a novel approach for measuring ARSB activities by incorporating tailor-made calibration curves according to each patient's DBS sample quenching properties. The second method is used to calculate ARSB activities by measuring the fluorescence and absorbance parameters in each reaction sample with a single DBS-free calibration curve.
  
  
  CONCLUSIONS
  The quantitative correlation between the DBS sample absorbance and its quenching effect can be used to calculate predictive ARSB activities and would serve as an affordable first tier screening test. The method described herein demonstrates the critical importance of adapting the β-MU calibration curves to each patient's unique DBS sample matrix and its positive impact on the accuracy and reliability of ARSB activity measurements.
authors.affiliation: Departamento de Química Biológica Patológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro E. Paladini" (IQUIFIB, UBA-CONICET), Buenos Aires, Argentina.
authors.forename: Paula G
authors.initials: PG
authors.lastname: Franco
authors.affiliation: Departamento de Química Biológica Patológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro E. Paladini" (IQUIFIB, UBA-CONICET), Buenos Aires, Argentina.
authors.forename: María J
authors.initials: MJ
authors.lastname: Pérez
authors.affiliation: Hospital General de Agudos Carlos G. Durand, Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Claudio
authors.initials: C
authors.lastname: Aranda
authors.affiliation: Departamento de Química Biológica Patológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro E. Paladini" (IQUIFIB, UBA-CONICET), Buenos Aires, Argentina.
authors.forename: Ana
authors.initials: A
authors.lastname: Adamo
authors.affiliation: Departamento de Química Biológica Patológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro E. Paladini" (IQUIFIB, UBA-CONICET), Buenos Aires, Argentina. Electronic address: lsilver81@yahoo.com.ar.
authors.forename: Lucas
authors.initials: L
authors.lastname: Silvestroff
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D059788:Dried Blood Spot Testing / Q000379:methods / Q000592:standards*; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009087:Mucopolysaccharidosis VI / Q000097:blood* / Q000175:diagnosis*; D020051:N-Acetylgalactosamine-4-Sulfatase / Q000097:blood* / Q000378:metabolism; D015203:Reproducibility of Results
chemical_list: D015415:Biomarkers; D020051:N-Acetylgalactosamine-4-Sulfatase
keywords: Arylsulfatase B; Enzyme activity; Fluorescence; Methylumbelliferone; Newborn screening; Quenching