DETOXIFICATION MECHANISMS IN SCHISTOSOMA MANSONI. CLONING AND CHARACTERIZATION OF A GST OMEGA

GIRARDINI J.E.; AMIRANTE A.; ZEMZOUMI K; SERRA E.

Carlos Paz, Argentina

Congreso; XXVII Reunión Anual de la Sociedad Argentina de Bioquímica y Biología molecular - SAIB; 2001

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.1pt 792.1pt; margin:36.0pt 315.9pt 36.0pt 36.0pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Schistosoma mansoni is ahuman parasite responsible for one of the most important endemics in the world. The parasite counts on different detoxification mechanisms acting against the chemical stress produced by the host. The superfamily of glutathion-S-trans­ferases (GSTs) includes several enzymes able to catalyze the con­jugation of glutathion (GSH) to different substrates. The enzymes are widespread among the species and are organized in classes with defined properties. Recently a new class of GSTs was defined and named omega. The enzymes belonging to this class present thiol transferase and GSH dihidroascorbate reductase activities. They do not have activity against classical substrates of other GSTs. Most ofthis enzymes are related to response to stress situations. Particu­larly interesting is the enzyme from mouse which was isolated from a cellline resistant to ionizing radiation and chemotherapeutic drugs. Using a semi nested PCR strategy to amplify cDNA ITom S. mansoni we isolated a sequence coding for a protein similar to some GSTs. The phylogenetic analysis allowed us to include it in the omega class. The analysis by RT-PCR and western blot, showed that the expression levels grow during the infection of the host and that they are higher in adult males. The enzyme was expressed in Es­cherichia coli. The recombinant enzyme showed glutathion dihidroascorbate reductase activity and no activity with DCNB or CDNB. The enzyrne binds S-hexyl glutathion with stronger affin­ity than GSH.