Presence of two new fatty acid binding proteins in catfish liver

A basic fatty acid binding protein (FABP), closely related to that of chicken liver, was isolated and characterized from catfish (Rhamdia sapo) liver in a previous work. Results herein show the presence of another two FABPs in which partial amino acid sequences reveal great similarity with the corresponding sequences of other already known FABPs belonging to the heart type. The purification procedures for both proteins involve gel filtration, anion-exchange chromatography, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (as a last step). Because both FABP N-termini were blocked, they were submitted to in-gel tryptic digestion and the resulting peptides were separated by high performance liquid chromatography, and sequenced by Edman degradation. One of these proteins presented the highest identity percentage when compared with those of the human and bovine heart and bovine brain (81%), and the other when compared with those of chicken retina (75%) and mouse and bovine heart FABP (70%). The presence of several FABPs plus the fact that they belong to different types, as found in the Rhamdia sapo liver, is unusual in mammals, which express a characteristic liver-type member of this protein family.