The amino acid sequence of a lamprey (Entosphenus japonicus) liver fatty acid-binding protein identified its close relationship to cardiac fatty acid-binding proteins of Mammalia

Fatty acid-binding proteins (FABPs) constitute a large, tissue-specific mul tigene family in animals. While liver FABPs of Aves, Reptilia. and Amphibia are close homologs of mammalian liver FABPs, the shark liver protein belon gs to the mammalian heart FABP subfamily. We purified an FABP from the live r of lamprey, Entosphenus japonicus, by gel filtration and anion-exchange c hromatography. Amino acid sequences determined for lysyl endopeptidase pept ides covered nearly the entire molecule except for N- and C-terminal short segments. Examination of the phylogenetic relationship from the sequence id entified the lamprey liver protein as a member of mammalian heart-type FABP s. Since livers of bony fish contain both hepatic and cardiac FABPs, expres sion of the FABP gene in the vertebrate liver appears to change from the he art-type to liver-type within Pisciformes. with bony fish being in a transi tion stage. This may be related to the evolutionary and physiological diver gence of liver function and lipid metabolism of these lower vertebrates. (C ) 1999 Elsevier Science Inc. All rights reserved.