Role of functional blocks in the evolution of exotrophy in vertebrates (as exemplified by fish and mammals)

The review reports the data on the presence in fish and mammals of the identical elementary or universal functional blocks (FBs)—molecules and supramolecular complexes providing exotrophic processes, with a special focus on those involved in the regulation of feeding behavior, digestion and transport of nutrients. When describing FBs implementing symbiotic digestion and induced autolysis, the data on the bacterial and mammalian enzymes have been analyzed. It is assumed that the structural and functional similarity of FBs in different organisms, which maintains the existence of trophic networks, is based on the need to perform similar functions and hence to develop similar mechanisms of FB adaptation in organisms phylogenetically distant from each other (bacteria, invertebrates, fish and mammals).