Comparison of maltose and acarbose as inhibitors of maltase-glucoamylase activity in assaying acid α-glucosidase activity in dried blood spots for the diagnosis of infantile Pompe disease

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Abstract

Purpose:

The study’s purpose was to compare acarbose and maltose as inhibitors of maltase-glucoamylase activity for determining acid α-glucosidase activity in dried blood spot specimens for early identification of patients with infantile Pompe disease, a severe form of acid α-glucosidase deficiency.

Methods:

Acid α-glucosidase activities in dried blood spot extracts were determined fluorometrically using the artificial substrate 4-methylumbelliferyl-α-D-pyranoside. Acarbose or maltose was used to inhibit maltase-glucoamylase, an enzyme present in polymorphonuclear neutrophils that contributes to the total α-glucosidase activity at acidic pH.

Results:

Complete discrimination between patients with proven infantile Pompe disease (n = 20), obligate heterozygotes (n = 16), and controls (n = 150) was achieved using 8 μmol/L acarbose as the inhibitor. Higher acarbose concentration (80 μmol/L) did not improve the assay. By using 4 mM maltose as the inhibitor, heterozygotes and patients were not completely separated. The results using acarbose compared well with those using the skin fibroblast assay in the same group of patients with proven infantile Pompe disease.

Conclusion:

Acid α-glucosidase activity measurements in dried blood spot extracts can reliably detect infantile Pompe disease in patients. The convenience of collecting and shipping dried blood specimens plus rapid turnaround time makes this assay an attractive alternative to established methods.

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