Submitted on June 5, 2006
Revised on September 5, 2006
Accepted on September 5, 2006
Biochemical and structural comparative study between bird and mammal pancreatic colipases
Abir Ben Bacha, Fakher Frikha, Ikram Djemal, Ahmed Fendri, Nabil Miled, Youssef Gargouri, and Hafedh Mejdoub
génie biologique, ENIS, Sfax 3038
Corresponding Author: ytgargouri{at}yahoo.fr
Three colipases were purified from pancreases of two birds (ostrich and turkey) and one mammal (dromedary). After acidic and/or heat treatment and precipitation by sulphate ammonium then ethanol, cofactors were purified by Sephadex G-50 gel filtration followed by two ion exchange chromatographies on Mono S then on Mono Q. One molecular form was obtained from each species with a molecular mass of about 10 kDa. Cofactors were not glycosylated. The determination of the N-terminal sequences of the three purified cofactors showed a high sequence homology. A 90 amino acid sequence of the ostrich cofactor was established based on peptide sequences from four different digests of the denaturated protein using trypsin, chymotrypsin, thermolysin or staphylococcal protease. This sequence exhibited a high degree of homology with chicken and mammal cofactors. Bile salt inhibited pancreatic lipases from five species were activated to variable extents by colipases from bird and mammal origins. The bird pancreatic lipase-colipase system appears to be functionally similar to homologous lipolytic systems from higher mammals. Our comparative study showed that mammal colipase presents lower activation level towards bird lipases than the bird counterpart. 3D modelling of ostrich colipase suggested a structural explanation of this fact.
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