Characteristics and Composition of Pepsins from Atlantic Cod

  • Asbjorn Gildberg
  • Ragnar L. Olsen
  • Jon B. Bjarnason
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 306)


Three pepsins have been purified from the gastric mucosa of Atlantic cod (Gadus morhua). The enzymes were denominated Pepsin I and Pepsin IIa and IIb. Pepsin I is a 35.5 kDa neutral protein (pI 6.9), whereas Pepsin IIa and IIb are 34 kDa acidic proteins (pI 4.0 and 4.1, respectively). Apparently, all three pepsins are glycosylated. The cod pepsins resemble bovine cathepsin D in being unable to hydrolyze N-acetyl-L-Phenylalanyl-3,5-diiodo-L-Tyrosine, a dipeptide used as substrate for mammalian pepsins. With hemoglobin as a substrate, they expressed lower catalytic efficiency than porcine pepsin. The apparent substrate affinity of the cod pepsins was substantially higher at pH 3.5 than at pH 2. N-terminal sequence analyses of cod pepsins indicate a significant evolutionary gap between fish and mammalian pepsins. A comparative evaluation of the results obtained indicate that fish pepsins may constitute an intermediate stage in a genetic evolution from cathepsin D to mammalian pepsin.


Aspartic Proteinase Amino Acid Sequence Analysis Porcine Pepsin Lower Catalytic Efficiency Cystine Content 
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Copyright information

© Plenum Press, New York 1991

Authors and Affiliations

  • Asbjorn Gildberg
    • 1
  • Ragnar L. Olsen
    • 1
  • Jon B. Bjarnason
    • 2
  1. 1.Norwegian Institute of Fisheries and AqucultureTromsoNorway
  2. 2.Science InstituteUniversity of IcelandReykjavikIceland

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