New insights into the fatty acid-binding protein (FABP) family in the small intestine

The fatty acid-binding protein (FABP) superfamily is constituted by 14-15 kDa soluble proteins which bind with a high affinity either long-chain fatty acids (LCFAs), bile acids (BAs) or retinoids. In the small intestine, three different FAB isoforms exhibiting a high affinity for LCFAs and/or BAs are expressed: the intestinal and the liver-type (I-FAB and L-FABP) and the ileal bile acid-binding protein (I-BABP). Despite of extensive investigations, their respective physiological function(s) are not clearly established. In contrast to the I-FAB, L-FAB and I-BABP share several common structural features ( shape, size and volume of the hydrophobic pocket). Moreover, L-FAB and I-BABP genes are also specifically regulated by their respective preferential ligands through a very similar molecular mechanism. Although, they exhibit differences in their binding specificities and location along the small intestine supporting a specialization, it is likely that L-FABP and I-BABP genes exert the same type of basic function(s) in the enterocyte, in contrast to I-FAB.