Trypsin and trypsinogen from an Antarctic fish: molecular basis of cold adaptation.

Trypsin from Antarctic fish Paranotothenia magellanica displays molecular and kinetic properties typical of enzymes produced by psychrophilic organisms. The enzyme has a high catalytic efficiency at low and moderate temperatures and is rapidly inactivated at temperatures higher than 30 degrees C. The nucleotide sequence was determined after mRNA extraction and cDNA synthesis. The cDNA encodes a pretrypsinogen which includes a seven residue activation peptide containing only three acidic residues preceeding the 222 amino-acid mature enzyme. A three-dimensional model of the enzyme was built. Structural parameters possibly involved in the adaptation to cold have been derived from comparison with the three-dimensional structure of the bovine enzyme. Among them are the lack of Tyr-151 in the substrate binding pocket, an overall decrease in the number of salt bridges and hydrophobicity and the increase in the surface hydrophilicity.