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

Abstract

Purpose: The study's purpose was to compare acarbose and maltose as inhibitors of maltase-glucoamylase activity for determining acid ␣-glucosidase activity in dried blood spot specimens for early identification of patients with infantile Pompe disease, a severe form of acid ␣-glucosidase deficiency. Methods: Acid ␣-glucosidase activities in dried blood spot extracts were determined fluorometrically using the artificial substrate 4-methylumbelliferyl-␣-D-pyranoside. Acarbose or maltose was used to inhibit maltase-glucoamylase, an enzyme present in polymorphonuclear neutrophils that contributes to the total ␣-glucosidase activity at acidic pH. Results: Complete discrimination between patients with proven infantile Pompe disease (n ϭ 20), obligate heterozygotes (n ϭ 16), and controls (n ϭ 150) was achieved using 8 mol/L acarbose as the inhibitor. Higher acarbose concentration (80 mol/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 ␣-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. Genet Med 2006:8(5):302-306.

Multiplex Enzyme Assay Screening of Dried Blood Spots for Lysosomal Storage Disorders by Using Tandem Mass Spectrometry

“…With the fluorogenic substrate 4-methylumbelliferyl-␣-glucoside, acarbose concentrations of 3-9 mol/L are sufficient to inhibit maltase glucoamylase activity in the assay (8,9 ). We found that with the synthetic substrate in this assay, 8 mol/L acarbose provided sufficient inhibition of maltase glucoamylase and maintenance of GAA activity (Supplemental Fig.…”

Digital Microfluidic Platform for Multiplexing Enzyme Assays: Implications for Lysosomal Storage Disease Screening in Newborns

“…Individual 3-mm DBS punches obtained from NBS cards and DBS cards from the control and patient groups were assayed for Pompe and Fabry diseases using benchtop fluorometry methods previously described (7,8,15,21 ). All procedures were carried out according to standard operating procedures in the Duke BGL, which is a College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendment (CLIA) certified clinical laboratory.…”

“…Other state programs (in Illinois, Missouri, and New Mexico) have recently mandated screening for certain LSDs. Using a modified version (15 ) of the fluorometric assay introduced by Chamoles et al (8 ), the NBS program in Taiwan has screened 206 088 newborns for Pompe disease (16 ) and 171 977 for Fabry disease (17 ). A recently published review article provides a nice overview of the current state of NBS for LSDs (18 ).…”

Lysosomal storage diseases: Diagnostic confirmation and management of presymptomatic individuals

“…49 -51 GAA activity can be either measured using fluorometry or tandem mass spectrometry (MS/MS). 49,50,52,53 Although there is a correlation between GAA activity in fibroblasts and clinical phenotype, the clinical phenotype may not be readily predicted through enzyme analysis in different tissues. 54 Serum creatine kinase, transaminases, and lactate dehydrogenase are increased in most patients with PD but may occasionally be within normal limits in those with adult-onset PD.…”