Assays / Genetic Enzymes / a-Mannosidase

Principle of Method:
Hydrolysis of the synthetic substrate 4-methylumbelliferyl-a-D-mannopyranoside at acid pH is followed by measuring the fluorescence of the liberated 4-methylumbelliferone after stopping the reaction with alkaline buffer.

Uses and Limitations of the Method:
Deficiency of lysosomal á-mannosidase is the primary defect in a-mannosidosis, leading to storage of various oligosaccharides with an a-mannose residue at their non-reducing terminals. a-mannosidase is elevated in plasma from patients with I-cell disease and pseudo-Hurler polydystrophy , and is a useful enzyme to measure in amniotic fluid for prenatal diagnosis of these disorders.

Prenatal diagnosis of a-mannosidosis is available by CVS or amniocentesis. Heterozygote detection may be possible in affected families but is not offered for screening in the general population.

a-mannosidosis patients exhibit a distinctive abnormal oligosacchariduria, and this is a good screening test before definitive assay of the enzyme. Assay of a-mannosidase is included in all our lysosomal enzyme screening procedures.

Specimen Requirements:
Blood. 5 ml lithium heparin (orange capped tube) unseparated and unfrozen. Send at room temperature to arrive at the laboratory within 24h of venepuncture.

THE LABORATORY RECOMMENDS USE OF A COURIER SERVICE OR ROYAL MAIL SPECIAL DELIVERY FOR SENDING ALL SPECIMENS TO THE LABORATORY.

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