Cathepsin D is a lysosomal aspartic proteinase that has been implicate
d in several pathological processes such as breast cancer and Alzheime
r's disease, We designed and synthesized a number of quenched fluoroge
nic substrates with P2 variations in the series AcEE(EDANS)KPIXFFRLGK(
DABCYL)E-NH2, where X=cysteine, methylcysteine, ethylcysteine, tert-bu
tylcysteine, carboxymethylcysteine, methionine, valine or isoleucine,
Most of the fluorogenic substrates exhibited greater k(cat)/K-m ratios
than the best cathepsin D substrates described so far, Differences in
kinetic constants, which were rationalized using structure-based mode
ling, might make certain substrates useful for particular applications
, such as active site titrations or initial velocity determination usi
ng a fluorescent plate reader, (C) 1997 Federation of European Biochem
ical Societies.