Fluorimetric assays for N-acetylgalactosamine-6-sulfatase and arylsulfatase B based on the natural substrates for confirmation of mucopolysaccharidoses types IVA and VI.

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.

• Authors: Arun Babu Kumar, Zdenek Spacil, Farideh Ghomashchi, Sophia Masi, Tomomi Sumida, Makoto Ito, Frantisek Turecek, C Ronald Scott, Michael H Gelb
• Journal: Clinica chimica acta; international journal of clinical chemistry (Clin Chim Acta) Vol. 451 Issue Pt B Pg. 125-8 (Dec 07 2015) ISSN: 1873-3492 [Electronic] Netherlands
• PMID: 26282597 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Elsevier B.V. All rights reserved.

Chemical References

• Biological Products
• Chondroitinsulfatases
• N-Acetylgalactosamine-4-Sulfatase
• ARSB protein, human
• GALNS protein, human

Topics

• Biological Products (metabolism)
• Chondroitinsulfatases (analysis, metabolism)
• Dried Blood Spot Testing
• Enzyme Assays
• Fluorometry
• Humans
• Infant, Newborn
• Mucopolysaccharidoses (classification, diagnosis, enzymology)
• N-Acetylgalactosamine-4-Sulfatase (analysis, metabolism)
• Neonatal Screening
• Protein Conformation
• Substrate Specificity