marine sponge.
The primary, secondary, and tertiary structures of ASPE were
determined by high-resolution 2D NMR spectroscopy (900
MHz). With the exception of an N-terminal modification, ASPE
shares properties with the previously reported asteropsins A−D,
that is, the absence of basic residues, a highly acidic nature,
conserved structurally important residues (including two cisprolines),
and a highly conserved tertiary structural framework.
ASPE was found to be remarkably stable to gastrointestinal tract
enzymes (chymotrypsin, elastase, pepsin, and trypsin) and to
human plasma