Amino Acid Sequence, Binding Properties and Evolutionary Relationships of the Basic Liver Fatty‐Acid‐Binding Protein from the Catfish Rhamdia sapo

The complete amino acid sequence of a basic liver fatty acid‐binding protein (L‐FABP) from catfish (Rhamdia sapo) was determined. Alignment of sequences shows that it has more similarity to chicken basic L‐FABP than to mammalian L‐FABP. The phylogenetic analysis suggests that basic L‐FABP from catfish, chicken and iguana diverged from the mammalian protein before the fish‐tetrapod divergence, thus implying that the two types are encoded by different genes. Supporting this conclusion, a 14‐kDa protein, structurally closely related to mammalian L‐FABP, was isolated from catfish intestine, indicating the presence of the two genes in the same species. The catfish basic L‐FABP binds only one fatty acid/molecule, while mammalian L‐FABP bind two. The former has more affinity for trans‐parinaric acid than for cis‐parinaric acid, in constrat to the latter proteins.