Arun Babu Kumar1, Zdenek Spacil1, Farideh Ghomashchi1, Sophia Masi1, Tomomi Sumida2, Makoto Ito2, Frantisek Turecek1, C Ronald Scott3, Michael H Gelb4. 1. Department of Chemistry, University of Washington, Seattle, WA 98195, USA. 2. Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8591, Japan. 3. Department of Pediatrics, University of Washington, Seattle, WA 98195, USA. 4. Department of Chemistry, University of Washington, Seattle, WA 98195, USA; Department of Biochemistry, University of Washington, Seattle, WA 98195, USA. Electronic address: gelb@chem.washington.edu.
Abstract
BACKGROUND: Treatments have been developed for mucopolysaccharidoses IVA (MPS IVA) and MPS VI suggesting the need for eventual newborn screening. Biochemical enzyme assays are important for diagnosis. Previously reported fluorimetric assays of the relevant enzymes are based on substrates with poor activity or specificity. METHODS: We developed new fluorimetric assays for N-acetylgalactosamine-6-sulfatase (GALNS) and arylsulfatase B (ARSB) based on the natural substrates, N-acetylgalactosamine-6-sulfate (and 4-sulfate), which have improved activity and specificity toward the relevant enzymes. The new substrates were tested on dried blood spots on newborn screening cards, and assays showed acceptable linearity in response with the amount of enzyme present (using quality control samples). RESULTS: When tested on dried blood spots from random newborns and affected patients, the assays showed good discrimination between the 2 sample groups. CONCLUSIONS: The analytical range of the new fluorimetric assays, defined as the ratio of enzyme-dependent-to-enzyme-independent assay response, is likely to be insufficient to use these assays for newborn screening. Rather, these new fluorimetric assays should be useful in a diagnostic lab to confirm a diagnosis via biochemical enzyme testing.
BACKGROUND: Treatments have been developed for mucopolysaccharidoses IVA (MPS IVA) and MPS VI suggesting the need for eventual newborn screening. Biochemical enzyme assays are important for diagnosis. Previously reported fluorimetric assays of the relevant enzymes are based on substrates with poor activity or specificity. METHODS: We developed new fluorimetric assays for N-acetylgalactosamine-6-sulfatase (GALNS) and arylsulfatase B (ARSB) based on the natural substrates, N-acetylgalactosamine-6-sulfate (and 4-sulfate), which have improved activity and specificity toward the relevant enzymes. The new substrates were tested on dried blood spots on newborn screening cards, and assays showed acceptable linearity in response with the amount of enzyme present (using quality control samples). RESULTS: When tested on dried blood spots from random newborns and affected patients, the assays showed good discrimination between the 2 sample groups. CONCLUSIONS: The analytical range of the new fluorimetric assays, defined as the ratio of enzyme-dependent-to-enzyme-independent assay response, is likely to be insufficient to use these assays for newborn screening. Rather, these new fluorimetric assays should be useful in a diagnostic lab to confirm a diagnosis via biochemical enzyme testing.
Authors: O P van Diggelen; H Zhao; W J Kleijer; H C Janse; B J Poorthuis; J van Pelt; J P Kamerling; H Galjaard Journal: Clin Chim Acta Date: 1990-02-28 Impact factor: 3.786
Authors: Mehmet Umut Akyol; Tord D Alden; Hernan Amartino; Jane Ashworth; Kumar Belani; Kenneth I Berger; Andrea Borgo; Elizabeth Braunlin; Yoshikatsu Eto; Jeffrey I Gold; Andrea Jester; Simon A Jones; Cengiz Karsli; William Mackenzie; Diane Ruschel Marinho; Andrew McFadyen; Jim McGill; John J Mitchell; Joseph Muenzer; Torayuki Okuyama; Paul J Orchard; Bob Stevens; Sophie Thomas; Robert Walker; Robert Wynn; Roberto Giugliani; Paul Harmatz; Christian Hendriksz; Maurizio Scarpa Journal: Orphanet J Rare Dis Date: 2019-06-13 Impact factor: 4.123