Other enzyme substrates

EDANS (EDANS acid [5-((2-Aminoethyl)amino)naphthalene-1-sulfonic acid]) is a novel and quenched fluorogenic substrate for assaying retroviral protease by resonance energy transfer (RET).

5-Bromo-4-chloro-3-indoxyl-beta-D-cellobioside is a chromogenic compound used to detect cellobiohydrolases.

4-Methylumbelliferyl β-D-Galactopyranoside-6-sulfate (sodium salt) (4-MU-Gal-6S) is a fluorogenic substrate used to quantify N-acetylgalactosamine-6-sulphatase (GALNS) activity. 4-MU-Gal-6S is cleaved by GALNS to release the fluorescent moiety 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 detect Morquio disease type A, a lysosomal storage disorder in which GALNS is deficient. 4-MU-Gal-6S can be used to assess GALNS activity in a very small blood volume to determine the extent of deficiency.