Comparison of maltose and acarbose as inhibitors of maltase-glucoamylase activity in assaying acid alpha-glucosidase activity in dried blood spots for the diagnosis of infantile Pompe disease.
OBJECTIVE
The study's purpose was to compare acarbose and maltose as inhibitors of maltase-glucoamylase activity for determining acid alpha-glucosidase activity in dried blood spot specimens for early identification of patients with infantile Pompe disease, a severe form of acid alpha-glucosidase deficiency.


METHODS
Acid alpha-glucosidase activities in dried blood spot extracts were determined fluorometrically using the artificial substrate 4-methylumbelliferyl-alpha-D-pyranoside. Acarbose or maltose was used to inhibit maltase-glucoamylase, an enzyme present in polymorphonuclear neutrophils that contributes to the total alpha-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 micromol/L acarbose as the inhibitor. Higher acarbose concentration (80 micromol/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.


CONCLUSIONS
Acid alpha-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.
Zhang
Haoyue
H
Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC 27709, USA.
Kallwass
Helmut
H
Young
Sarah P
SP
Carr
Cortney
C
Dai
Jian
J
Kishnani
Priya S
PS
Millington
David S
DS
Keutzer
Joan
J
Chen
Yuan-Tsong
YT
Bali
Deeksha
D
D020909:Acarbose / Q000494:pharmacology; D000328:Adult; D004796:Clinical Enzyme Tests / Q000379:methods*; D004791:Enzyme Inhibitors; D006009:Glycogen Storage Disease Type II / Q000175:diagnosis*; D065089:Glycoside Hydrolase Inhibitors; D006579:Heterozygote; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D008320:Maltose / Q000494:pharmacology; D000520:alpha-Glucosidases / Q000097:blood
D004791:Enzyme Inhibitors; D065089:Glycoside Hydrolase Inhibitors; D008320:Maltose; C509951:GAA protein, human; D000520:alpha-Glucosidases; D020909:Acarbose