Journal of Inherited Metabolic Disease

, Volume 32, Issue 3, pp 416–423

Enzyme analysis for Pompe disease in leukocytes; superior results with natural substrate compared with artificial substrates

Authors

    • Department of Clinical GeneticsErasmus University Medical Centre
    • Department of Clinical GeneticsErasmus MC
  • L. F. Oemardien
    • Department of Clinical GeneticsErasmus University Medical Centre
  • N. A. M. E. van der Beek
    • Department of NeurologyErasmus University Medical Centre
  • M. A. Kroos
    • Department of Clinical GeneticsErasmus University Medical Centre
  • H. K. Wind
    • Department of ImmunologyErasmus University Medical Centre
  • Y. V. Voznyi
    • Institute of Organic Chemistry
  • D. Burke
    • The Enzyme Laboratory, Department of Chemical PathologyGreat Ormond Street Hospital
  • M. Jackson
    • Supra-regional Assay Service for Genetic Enzyme DefectsGuys Hospital
  • B. G. Winchester
    • Biochemistry Research Group, UCL Institute of Child HealthUniversity College London
  • A. J. J. Reuser
    • Department of Clinical GeneticsErasmus University Medical Centre
Original Article

DOI: 10.1007/s10545-009-1082-3

Cite this article as:
van Diggelen, O.P., Oemardien, L.F., van der Beek, N.A.M.E. et al. J Inherit Metab Dis (2009) 32: 416. doi:10.1007/s10545-009-1082-3

Summary

Enzyme analysis for Pompe disease in leukocytes has been greatly improved by the introduction of acarbose, a powerful inhibitor of interfering α-glucosidases, which are present in granulocytes but not in lymphocytes. Here we show that the application of acarbose in the enzymatic assay employing the artificial substrate 4-methylumbelliferyl-α-d-glucoside (MU-αGlc) is insufficient to clearly distinguish patients from healthy individuals in all cases. Also, the ratios of the activities without/with acarbose only marginally discriminated Pompe patients and healthy individuals. By contrast, when the natural substrate glycogen is used, the activity in leukocytes from patients (n = 82) with Pompe disease is at most 17% of the lowest control value. The use of artificial substrate in an assay with isolated lymphocytes instead of total leukocytes is a poor alternative as blood samples older than one day invariably yield lymphocyte preparations that are contaminated with granulocytes. To diagnose Pompe disease in leukocytes we recommend the use of glycogen as substrate in the presence of acarbose. This assay unequivocally excludes Pompe disease. To also exclude pseudo-deficiency of acid α-glucosidase caused by the sequence change c.271G>A (p.D91N or GAA2; homozygosity in approximately 1:1000 caucasians), a second assay employing MU-αGlc substrate plus acarbose or DNA analysis is required.

Abbreviations

DBS

dried blood spot on filter paper

GSD II

glycogen storage disease type II, Pompe disease, acid maltase deficiency

Glcn

Glycogen

MU

4-methylumbelliferone

MU-αGlc

4-methylumbelliferyl-α-d-glucoside

NEM

N-ethylmaleimide

Copyright information

© Springer Science+Business Media B.V. 2009