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D. Lemos et al.rAquaculture 186 (2000 89–105 97
digestive potential through larval development may be a clue to assess optimal nutri-
tional conditions for cultured penaeid species ŽJones et al., 1997 .
.
As observed for enzyme activity, the characteristics of digestive proteinases may also
vary during the early stages of penaeid species ŽFang and Lee, 1992; Lemos et al.,
1999 .. The number of enzymes, isoenzymes and their molecular weight, as demonstrated
by substrate-SDS-PAGE, varies significantly through ontogenetic development of F.
paulensis ŽLemos et al., 1999 Fig. 3 . Intense activity zones of 16.4 to 19.5 kDa were
. Ž
.
observed in protozoea II and mysis I. The number of active bands Ž14.6, 16.4, 17.5,
19.5, 22.5, 23.9, 25.8, 28.9, 32.0, 34.4, 37.7 and 42.2 kDa . was higher in adults
compared to early stages and may be due to an increase in cellular and physiological
complexity of the digestive gland during development ŽMorgan et al., 1978; Biesiot and
Capuzzo, 1990; Dall et al., 1990 .. The characterization of digestive enzymes involves
determining their specificity and kinetic properties. The importance of a given enzyme
to shrimp digestion can be quantitatively assessed after its identification and characteri-
zation. For aquaculture purposes, the variation in the proteinase pattern between
postlarva and adult ŽFig. 3 shows these stages may have different nutritional require-
.
ments, and possibly a need for specific feeds.
Trypsin and chymotrypsin fractions can be identified in SDS-PAGE by using
synthetic proteinase inhibitors ŽFig. 4 . However, the proteinases of F. paulensis were
.
not inhibited by tosyl-phenylalanine chloromethyl ketone, lane 3 ŽTPCK , an inhibitor of
.
mammalian chymotrypsin ŽFig. 4 . TLCK is a trypsin inhibitor and PMSF is a specific
.
serine proteinase inhibitor. Since trypsin and chymotrypsin are serine proteinases, active
bands inhibited by both TLCK and PMSF were considered as trypsin while the
inhibition by PMSF only may be an evidence of chymotrypsin. Four trypsins from 14.6

Fig. 3. Digestive proteinases of different ontogenetic stages of Farfantepenaeus paulensis in substrate-SDS-
PAGE ŽLemos et al., 1999 . MWsmolecular weight markers, Abbreviations as in Fig. 2.
.