Fan Yi1, Xinying Hong1, Arun Babu Kumar1, Chengli Zong2, Geert-Jan Boons2, C Ronald Scott3, Frantisek Turecek1, Bruce H Robinson1, Michael H Gelb4. 1. Department of Chemistry, Bagley Hall, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States. 2. University of Georgia's Complex Carbohydrate Research Center, 315 Riverbend Road, Athens, GA 30602, United States. 3. Department of Pediatrics, RR 310 Health Science Building, University of Washington, Box 356320, Seattle, Washington 98195-6320, United States. 4. Department of Chemistry, Bagley Hall, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States; Department of Biochemistry, University of Washington, Box 357350, Seattle, WA 98195-7350, United States. Electronic address: gelb@chem.washington.edu.
Abstract
BACKGROUND: With ongoing efforts to develop improved treatments for Sanfilippo Syndrome Type A (MPS-IIIA), a disease caused by the inability to degrade heparan sulfate in lysosomes, we sought to develop an enzymatic activity assay for the relevant enzyme, sulfamidase, that uses dried blood spots (DBS). METHODS: We designed and synthesized a new sulfamidase substrate that can be used to measure sulfamidase activity in DBS using liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: Sulfamidase activity was readily detected in DBS using the new substrate and LC-MS/MS. Sulfamidase activity showed acceptable linearity proportional to the amount of enzyme and reaction time. Sulfamidase activity in 238 random newborns was well elevated compared to the range of activities measured in DBS from 8 patients previously confirmed to have MPS-IIIA. CONCLUSIONS: This is the first report of an assay capable of detecting sulfamidase in DBS. The new assay could be useful in diagnosis and potentially for newborn screening of MPS-IIIA.
BACKGROUND: With ongoing efforts to develop improved treatments for Sanfilippo Syndrome Type A (MPS-IIIA), a disease caused by the inability to degrade heparan sulfate in lysosomes, we sought to develop an enzymatic activity assay for the relevant enzyme, sulfamidase, that uses dried blood spots (DBS). METHODS: We designed and synthesized a new sulfamidase substrate that can be used to measure sulfamidase activity in DBS using liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: Sulfamidase activity was readily detected in DBS using the new substrate and LC-MS/MS. Sulfamidase activity showed acceptable linearity proportional to the amount of enzyme and reaction time. Sulfamidase activity in 238 random newborns was well elevated compared to the range of activities measured in DBS from 8 patients previously confirmed to have MPS-IIIA. CONCLUSIONS: This is the first report of an assay capable of detecting sulfamidase in DBS. The new assay could be useful in diagnosis and potentially for newborn screening of MPS-IIIA.
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