IAL   21557
INSTITUTO DE AGROBIOTECNOLOGIA DEL LITORAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Study of enzymes involved in glycogen metabolism in Giardia lamblia
Autor/es:
EBRECHT, A.C.; GUERRERO, S.A.; IGLESIAS, A.A.
Lugar:
Chubut
Reunión:
Congreso; XLVI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010
Resumen:
Giardia lamblia is the etiological agent of giardiasis, an intestinal infection most prevalent in children. Research on this protozoon is driven both by its impact on public health and its relevance for understanding evolution of eukaryotes, since it is a member of one of the earliest diverging eukaryotic lineages. It is known that glucose is a key source of metabolic energy for the organism, being the monosaccharide accumulated as glycogen in the trophozoite stage. We cloned the genes coding for glycogen synthase (EC 2.4.1.11) and UDP-glucose pyrophosphorylase (EC 2.7.7.9; UDPGlcPPase) from genomic DNA of G. lamblia. The latter gene was expressed in heterologous cells (Escherichia coli), and the recombinant enzyme was purified and characterized in its kinetic properties. GlaUDPGlcPPase exhibited typical hyperbolic saturation kinetics for substrates, with Km values of 0.13 mM (UTP), 0.14 mM (Glc1P) and 0.55 mM (Mg2+). The enzyme was inactivated by oxidants as diamide, hydrogen peroxide and sodium nitroprusside. The inactivation was reversed by reducing agents: DTT and thioredoxin (from Entamoeba histolytica and Trypanosoma brucei). Results support the occurrence of a physiological redox mechanism for modulation of UDPGlcPPase activity in protozoa (and other eukaryotes). Such a mechanism would be critical to regulate carbohydrates metabolism and to determine virulence in G. lamblia.