4-Methylumbelliferyl-β-D-glucuronide hydrate (MUG)

Prenatal Diagnosis of Tay-Sachs Disease

Tay-Sachs disease (TSD) is an autosomal recessive lysosomal storage disorder caused by mutations of the HEXA gene resulting in the deficiency of hexosaminidase A (Hex A) and subsequent neuronal accumulation of GM2 gangliosides. Infantile TSD is a devastating and fetal neurodegenerative disease with death before the age of 3-5 years. A small proportion of TSD patients carry milder mutations and may present juvenile or adult onset milder disease. TSD is more prevalent among Ashkenazi Jewish (AJ) individuals and some other genetically isolated populations with carrier frequencies of approximately ~1:27 which is much higher than that of 1:300 in the general population. Carrier screening and prenatal testing for TSD are effective in preventing the birth of affected fetuses greatly diminishing the incidence of TSD. Testing of targeted HEXA mutations by genotyping or sequencing can detect 98% of carriers in AJ individuals; however, the detection rate is much lower for most other ethnic groups. When combined with enzyme analysis, above 98% of carriers can be reliably identified regardless of ethnic background. Multiplex PCR followed by allele-specific primer extension is one method to test for known and common mutations. Sanger sequencing or other sequencing methods are useful to identify private mutations. For prenatal testing, only predefined parental mutations need to be tested. In the event of unknown mutational status or the presence of variants of unknown significance (VUS), enzyme analysis must be performed in conjunction with DNA-based assays to enhance the diagnostic accuracy. Enzymatic assays involve the use of synthetic substrates 4-methylumbelliferyl-N-acetyl-β-glucosamine (4-MUG) and 4-methylumbelliferyl-6-sulfo-2-acetamido-2-deoxy-β-D-glucopyranoside (4-MUGS) to measure the percentage Hex A activity (Hex A%) and specific Hex A activity respectively. These biochemical and molecular tests can be performed in both direct specimens and cultured cells from chorionic villi sampling or amniocentesis.

4-Methylumbelliferyl glucuronide contributes to hyaluronan synthesis inhibition

4-Methylumbelliferone (4-MU) inhibits hyaluronan (HA) synthesis and is an approved drug used for managing biliary spasm. However, rapid and efficient glucuronidation is thought to limit its utility for systemically inhibiting HA synthesis. In particular, 4-MU in mice has a short half-life, causing most of the drug to be present as the metabolite 4-methylumbelliferyl glucuronide (4-MUG), which makes it remarkable that 4-MU is effective at all. We report here that 4-MUG contributes to HA synthesis inhibition. We observed that oral administration of 4-MUG to mice inhibits HA synthesis, promotes FoxP3⁺ regulatory T-cell expansion, and prevents autoimmune diabetes. Mice fed either 4-MUG or 4-MU had equivalent 4-MU:4-MUG ratios in serum, liver, and pancreas, indicating that 4-MU and 4-MUG reach an equilibrium in these tissues. LC-tandem MS experiments revealed that 4-MUG is hydrolyzed to 4-MU in serum, thereby greatly increasing the effective bioavailability of 4-MU. Moreover, using intravital 2-photon microscopy, we found that 4-MUG (a nonfluorescent molecule) undergoes conversion into 4-MU (a fluorescent molecule) and that 4-MU is extensively tissue bound in the liver, fat, muscle, and pancreas of treated mice. 4-MUG also suppressed HA synthesis independently of its conversion into 4-MU and without depletion of the HA precursor UDP-glucuronic acid (GlcUA). Together, these results indicate that 4-MUG both directly and indirectly inhibits HA synthesis and that the effective bioavailability of 4-MU is higher than previously thought. These findings greatly alter the experimental and therapeutic possibilities for HA synthesis inhibition.

Facile anomer-oriented syntheses of 4-methylumbelliferyl sialic acid glycosides

As part of a program to find new sialidases and determine their enzymatic specificity and catalytic activity, a library of 4-methylumbelliferyl sialic acid glycosides derivatised at the C-5 position were prepared from N-acetylneuraminic acid. Both α- and β-4-methylumbelliferyl sialic acid glycosides were prepared in high yields and stereoselectivity. α-Anomers were accessed via reagent control by utilising additive CH3CN and TBAI, whereas the β-anomers were synthesised through a diastereoselective addition reaction of iodine and the aglycone to the corresponding glycal followed by reduction of the resulting 3-iodo compounds. Both anomer-oriented synthetic pathways allow for gram-scale stereoselective syntheses of the desired C-5 modified neuraminic acid derivatives for use as tools to quantify the enzymatic activity and substrate specificity of known sialidases, and potential detection and investigation of novel sialidases.

Structure of 4-methylumbelliferyl-beta-D-glucopyranoside

C16H17O8.1.5H2O, Mr = 364.33, monoclinic, C2, a = 14.314 (3), b = 6.851 (1), c = 18.178 (5) A, beta = 100.90 (2) degrees, V = 1750.46 A3, Z = 4, D chi = 1.382 Mg m-3, lambda(Mo K alpha) = 0.71069 A, mu = 0.933 mm(-1), F(000) = 768, T = 294 K, R = 0.078 for all 2160 reflections. The structure is characterized by the close stacking along the b axis of the planar 4-methylumbelliferyl ring system which is nearly perpendicular to b and the extensive hydrogen bonding scheme in which all hydroxyl groups are within 2.95 A of at least two other O atoms.

4-Methylumbelliferyl 2-acetamido-2-deoxy-alpha-D-glucopyranoside, a fluorogenic substrate for N-acetyl-alpha-D-glucosaminidase

Condensation of dimeric 3,4,6-tri-O-acetyl-2-deoxy-2-nitroso-alpha-D-glucopyranosyl chloride with 4-methylumbelliferone gave crystalline 4-methylumbelliferyl 3,4,6-tri-O-acetyl-2-deoxy-2-oximino-alpha-D-arabino-hexopyranoside. Acetylation of this adduct, reduction of the resulting crude O-acetyloxime with borane in oxolane, and acetylation gave the 3,4,6-tri-O-acetyl derivative of 4-methylumbelliferyl 2-acetamido-2-deoxy-alpha-D-glucopyranoside (1). A new sensitive assay of N-acetyl-alpha-D-glucosaminidase (EC 3.2.1.50) is made possible by fluorometric measurement of 4-methylumbelliferone liberated by enzymic hydrolysis of glycoside 1. Such assays are illustrated by results obtained with enzyme preparations from pig liver and human-blood serum.