Determination of Reference Values for Alpha-N-Acetylglucosaminidase Activities in Patients with Sanfilippo Type B Disease and Control Population in Colombia

Abstract

Abstract Sanfilippo B is a lysosomal disorder characterized by the pathological accumulation of heparan sulfate. It is caused by mutations in the NAGLU gene that codes for the alpha-N-acetylglucosaminidase enzyme. The objective of this study was to determine the reference values and frequency of Sanfilippo B in Colombia through an enzyme analysis of leukocytes extracts. We aim to inform the community and the health system so that they can work in a preventive way, providing an early diagnosis of patients and thus providing an appropriate management of the symptoms. We carried out an endpoint assay that indirectly quantifies NAGLU activity through the cleavage of 4-methylumbelliferone from the 4-methylumbelliferyl-2-acetamido-2-deoxy-α-D-glucopyranoside substrate. The activity of 463 healthy volunteers (Range: 0.6 - 4 nmol/mg/h, Median: 1.69 +/- 0.73) as well as 462 patients referred for clinical suspicion, was calculated. From the last group, 7 cases turned out to be positive (Range: 0 - 0.24 nmol/mg/h, Median: 0.13 +/- 0.09). The cut-off point according to ROC analysis between affected patients and controls was 0.42 nmol/mg/h. To our knowledge, this study is the first in Colombia where an estimated frequency of Sanfilippo type B is calculated by providing enzyme activity ranges and a cut-off point.

Keywords

• mucopolysaccharidosis III
• heparan sulfate
• Sanfilippo syndrome B
• NAGLU deficiency
• fluorometric endpoint assay