In general, the spectral characteristics displayed by commercial
bromelain and purified, cryoprotected bromelain are typical of
a + b proteins, the CD signal of which is more intense at 210 nm
than at 223 nm, as was observed in the case of different fruit proteinases
such as papain and proteinase Q [48,49]. Thus it is probable
that bromelain forms may have the same folding pattern
shown in other members of the papain family, namely a bilobal
structure with all a-helical and b-sheet domains [50]. In spite of
the aforementioned similarities, fluorescence and CD curves for
purified, cryoprotected bromelain show one discreet dislocation
to the left at 200 nm when compared to commercial bromelain.
This discrepancy could be caused by the two N-acetylglucosamine
residues present in the carbohydrate moiety linked to the polypeptide
chain of bromelain that clearly appears in other fruit proteinases
such as papain and proteinase Q [49,51].