Direct assay of iduronate-2-sulfatase for Hunter disease using UPLC-tandem mass spectrometry and fluorogenic substrate

作者：Lee Kyunghoon; Jun Sun Hee; Song Sang Hoon; Park Hyung Doo; Park Kyoung Un; Song Junghan^*

来源：Clinical Biochemistry, 2015, 48(18): 1350-1353.

DOI：10.1016/j.clinbiochem.2015.08.016

• Mucopolysaccharidosis
• Hunter disease
• Tandem mass spectrometry
• Dried blood spot
• Newborn screening

Objective: We devised iduronate-2-sulfatase (IDS) enzyme activity assays by combining fluorometric substrate and LC-MS/MS based detection.
Design and methods: 4-Methylumbelliferyl alpha-L-idopyranosiduronic acid 2-sulfate (IDS-S) was used as a substrate for IDS. Its enzymatic product, 4-methylumbelliferyl alpha-L-idopyranosiduronic acid (IDS-P) and internal standard, 4-methylumbelliferyl alpha-L-idopyranoside (IDS-IS), were directly measured by UPLC-MS/MS. We determined the precision of our enzyme assay and the effects of sample amounts and incubation time based on the results. Dried blood spots (DBSs) of 110 normal newborns and three patients with Hunter disease were analyzed.
Results: IDS-IS, IDS-P and IDS-S were fully separated using UPLC without any ion suppressions. The intra- and inter-assay precisions were 8.5-10.5% and 11.9-15.3%, respectively. The amount of product obtained was proportional to the number of DBSs and increased linearly with the incubation period from 0 to 15 h. The enzyme activities in DBSs from three patients with MPS II were markedly lower than those in the DBSs of 110 normal newborns.
Conclusion: To the best of our knowledge, this is the first report describing the use of LC-MS/MS for the diagnosis of Hunter disease with a commercially available substrate. Our method would be a rapid and effective screening tool for the diagnosis of Hunter disease with further study.

• 出版日期2015-12