4-Methylumbelliferyl β-D-N,N'-diacetylchitobioside (4-μU-(GlcNAc)2) is a fluorogenic substrate for chitinases and chitobiosidases. 4-μU-(GlcNAc)2 is cleaved by chitinases and chitobiosidases to release the fluorescent moiety 4-μU. 4-μU fluorescence is pH-dependent with excitation maxima of 320 and 360 nm at low (1.97-6.72) and high pH (7.12-10.3), respectively, and an emission maximum ranging from 445 to 455 nm, increasing as pH decreases.
4-Methylumbelliferyl caprylate (MUCAP) is a fluorogenic substrate for C8 esterase. MUCAP is cleaved by C8 esterase to release the fluorescent moiety 4-methylumbelliferyl (4-MU). 4-MU fluorescence is pH-dependent with excitation maxima of 320 and 360 nm at low (1.97-6.72) and high (7.12-10.3) pH, respectively, and an emission maximum ranging from 445 to 455 nm, increasing as pH decreases.
Mu-6S-Palm-β-Glc is a fluorogenic substrate of palmitoyl-protein thioesterase (PPT, also known as CLN1), a lysosomal hydrolase that removes long-chain fatty acyl groups from modified cysteine residues in proteins. Mu-6S-Palm-β-Glc is cleaved by PPT CLN1 to release the fluorescent moiety 4-methylumbelliferyl (4-MU). 4-MU fluorescence is pH-dependent with excitation maxima of 320 and 360 nm at low (1.97-6.72) and high (7.12-10.3) pH, respectively, and an emission maximum ranging from 445 to 455 nM, increasing as pH decreases. This substrate is used in assays that measure PPT activity, which is commonly deficient in the neurodegenerative disorder known as infantile neuronal ceroid lipofuscinosis.
4-Methylumbelliferyl-2-acetamido-2-deoxy-β-D-glucopyranoside is a fluorogenic substrate for β-hexosaminidases. Upon enzymatic cleavage by β-hexosaminidases, 4-methylumbelliferone (4-μU) is released and its fluorescence can be used to quantify β-hexosaminidase activity. 4-MU fluorescence is pH-dependent with excitation maxima of 320 and 360 nm at low (1.97-6.72) and high pH (7.12-10.3), respectively, and an emission maximum ranging from 445 to 455 nm, increasing as pH decreases. 4-Methylumbelliferyl-2-acetamido-2-deoxy-β-D-glucopyranoside has been used to quantify β-hexosaminidase activity in serum or leukocytes from patients with GM2 gangliosidoses such as Tay-Sachs disease, which is characterized by defects in the α subunit of β-hexosaminidase.
4-Methylumbelliferyl-β-D-N,N',N''-triacetylchitotrioside is a fluorogenic substrate for chitinases and chitotriosidases. 4-Methylumbelliferyl-β-D-N,N',N''-triacetylchitotrioside is cleaved by chitinases and chitotriosidases to release the fluorescent moiety 4-methylumbelliferyl (4-MU). 4-MU fluorescence is pH-dependent with excitation maxima of 320 and 360 nm at low (1.97-6.72) and high (7.12-10.3) pH, respectively, and an emission maximum ranging from 445 to 455 nM, increasing as pH decreases. It has been used to screen plasma samples for reduced chitotriosidase activity that may be indicative of lysosomal storage disorders.