4-Methylumbelliferyl a-L-idopyranosiduronic acid 2-sulphate disodium salt;

4-MU-a-IdoA 2-sulfate; 4MU-a-L-iduronide-2-sulphate Na; M2;

4MU-alpha-L-iduronide-2-sulphate is a fluorogenic substrate for iduronate-2-sulphatase (IDS), used in a 2-step assay coupled with alpha-L-iduronidase. The assay is used in biochemical testing for Hunter syndrome (mucopolysaccharidosis II / MPS II). In a first step, iduronidate-2-sulphatase from biological samples cleaves the sulphate group from 4MU-alpha-L-iduronide-2-sulphate. In a second step, exogeneous alpha-L-iduronidase which cleaves the 4-MU moiety is added to the reaction, resulting in release of a fluorescent signal (Ex 360 nm / Em 455 nm). The reaction is stopped by the addition of sodium carbonate.

4-Methylumbelliferyl-α-L-iduronide 2-sulfate (4-MU-α-IdoA 2-sulfate) is a fluorogenic substrate of α-L-iduronidase that has been used in an assay to detect Hurler syndrome. It is also used as a substrate for iduronate-2-sulfatase in tests for Hunter disease. For these latter tests, the initial enzymatic product, 4-MU-α-IdoA can be measured by mass spectrometry, or it can be hydrolyzed with α-L-iduronidase to liberate the fluorophore 4-MU, which has an emission maximum at 445-454 nm. The excitation maximum for 4-MU is pH-dependent: 330, 370, and 385 nm at pH 4.6, 7.4, and 10.4, respectively.