Schistosoma mansoni is one of the most prevalent parasitic helminths that infect humans. Evidence for the presence of gluconeogenesis in S. mansoni was not observed until 1991, when the activity of four gluconeogenic enzymes was demonstrated in adult worms of S. mansoni. Two of those enzymes were carboxylases, which must contain biotin as prosthetic group in their structures. Later in 1997, biotin and biotinylated polypeptides were identified in cercária of S. mansoni. In this work, 2-D electrophoresis was used for the investigation of the presence of biotinylated polypeptides in adult worms of S. mansoni. The adult worms were obtained after 50 days of infection of the mice (Mus musculus) with 100 cercariae of SLM (São Lourenço da Mata) strain. The animals were sacrificed for the withdrawal of the adult worms, which were frozen with liquid nitrogen, ground to a fine powder and the proteins precipitated by the addition of 10% TCA in acetone, containing 20mM DTT. After centrifugation, the pellet was washed with cold acetone and resuspended in 8M urea, 4% CHAPS, 60mM DTT and 2% Immobilized pH gradient (IPG) buffer (pH 4-7).  IPG strip (7 cm) rehydration and Isoelectric focusing (IEF) were performed as recommended by the manufacture (GE Healthcare), followed by a 12.5 % SDS-PAGE. After the transference of proteins from the gel to nitrocellulose sheets, they were incubated at 4^oC, overnight with 1% BSA, streptavidin-HRP, for 30 min at room temperature and finally, incubated with the substrate tetra-methyl benzidine (TMB)-sodium dioctylsulfosuccinate. Several bands were identified in the range of 36 to 20 kD. Some well defined bands below 14 kD were also seen on the nitrocellulose. In conclusion of our preliminary results, we can speculate that adult worms of S. mansoni have some carboxylases not yet identified, whose functions will have to be studied.