H. Outzen et al., TEMPERATURE AND PH SENSITIVITY OF TRYPSINS FROM ATLANTIC SALMON (SALMO-SALAR) IN COMPARISON WITH BOVINE AND PORCINE TRYPSIN, Comparative biochemistry and physiology. B. Comparative biochemistry, 115(1), 1996, pp. 33-45
Four differently charged trypsins were purified from pyloric caeca of
Atlantic salmon (Salmo salar). The isoelectric points of three anionic
isoforms were 4.70, 4.60, and 4.55 (anionic trypsin I, II and III, re
spectively). And for the first time a cationic isoform (isoelectric po
int above 9.3) has been isolated from a marine species. The apparent m
olecular weights of all four isoforms were about 25 kDa as determined
by SDS-PAGE. The salmon enzymes were inhibited by serine proteinase in
hibitors in general and also by specific trypsin inhibitors. Anionic t
rypsin I and the cationic isoform were further examined. Anionic tryps
in I showed the typical cold-adaptation features, low pH and temperatu
re stability (also lower Gibb's free energy of GdnHCl-induced unfoldin
g) and high catalytic efficiency as compared to the mammalian trypsins
. The cationic isoform did not show these features, but resembled the
mammalian trypsins.