The recovered ML topology was very similar to the one generated by the NJ method, showing high conservation in vertebrates and in each insect order. The newly described S. frugiperda fut8 sequence grouped with other early diverging lepidopteran FUT8 sequences. Both tree topologies tended to place nematode FUT8 Dimaprit dihydrochloride sequences outside the protostome branch suggesting that these are rapidly evolving FUT8 sequences. We also investigated the extent of synteny and gene order conservation in the metazoan FUT8 sequences visualized at the Genomicus web site. This preliminary analysis suggested microsynteny conservation in each insect order and no synteny conservation between insect orders. FUT8 can be considered part of the GT-23 family within the CAZy classification, which groups enzymes acting on carbohydrates.This classification is based on the structural and mechanistic features of these glycosyltransferases. GT-23 is a single-copy nuclear gene family, whereas most GT families are polygenic. fut8 cDNAs have been cloned essentially from a few mammalian species and all essential aa residues implicated in FUT8 enzymatic activity were identified in the Sf9 FUT8 sequence. However, analysis of the cysteine residues involved in the disulfide bridges formation in most FUT8 DMH1 proteins shows that one cysteine residue, which corresponds to Cys-472 in human FUT8, is missing in the lepidopteran protein. This change is accompanied by the presence of a new cysteine residue that is also conserved in many FUT8 sequences. The high enzymatic activity measured with recombinant Sf9 FUT8 suggests that the disulfide bridge detected between Cys-465 and Cys-472 in most species can probably be equally established between Cys-465 with Cys-438 in S. frugiperda FUT8 without affecting its enzymatic activity or protein stability. Two potential N-glycosylation sites are also present in the Sf9 sequence, but these sites are not conserved in agreement with the fact that the enzyme activity is not dependent on the presence of N-glycans. In an attempt to trace back the origin and evolutionary relationships of fut8 genes, we identified fut8 orthologs in a large panel of metazoan genomes and determined their gene organization.