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Comparativemolecular analysis of evolutionary distant glyceraldehyde-3-phosphate dehydrogenases fromtwomarine species of fisheries interest, Sardina pilchardus and Octopus vulgaris

Tarik Baibai, Laila Oukhattar, Driss Mountassif, Omar Assobhei, Aurelio Serrano, Abdelaziz Soukri

The NAD+ dependent cytosolic glyceraldehyde-3-phosphate dehydrogenase (GAPDH,EC1.2.1.12), a key enzyme of central carbonmetabolismand bioenergetics, has been purified to homogeneity from muscle tissues of two distinctmarine species, skeletalmuscle of Sardina pilchardusWalbaum (Teleost, Clupeida) and arm incompressible muscle of Octopus vulgaris (Mollusca, Cephalopoda). Comparative biochemical studies revealed that the two proteins differ by their subunit molecular masses, pI values and exhibit some specific catalytic features. Partial cDNAsequences corresponding to an internal region of the GapC genes fromSardina andOctopuswere obtained by the polymerase chain reaction using degenerate primers constructed fromhighly conserved proteinmotifs.Alignments of deduced amino acid sequences were used to establish the 3D active site structures of the two enzymes as well as the phylogenetic relationships of the sardine and octopus enzymes, which are the first GAPDHs characterized so far from a teleost fish and a cephalopod, respectively. Interestingly, phylogenetic analyses place the sardine GAPDH in a cluster with the archetypical enzymes from other vertebrates, while the octopus GAPDHs comes together with other molluscan sequences, in a distant basal assembly closer to their bacterial and fungal homologs.