INVESTIGADORES
ISSOGLIO Federico Matias
congresos y reuniones científicas
Título:
REACTION MECHANISM AND GLUCOSYLATION EXTENT OF MONOMERIC AND DIMERIC GLYCOGENIN AUTOGLUCOSYLATION
Autor/es:
ISSOGLIO, FEDERICO M.; CARRIZO MARÍA E.; LAFI, IVANA; ROMERO, JORGE M.; CURTINO, JUAN A.
Lugar:
Buzios
Reunión:
Congreso; XXXVIII Annual Meeting of the Argentinean Biophysical Society 2009; 2009
Resumen:
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We
have recently described
that below 0.8-0.6 µM,
the concentration at which glycogenin exists as monomer, the enzyme
has the ability to autoglucosylate with a first order kinetics
(Biochem, Biophys. Res. Commun. 371:328-332, 2008). Thus, our results
indicated that the intersubunit glucosylation of dimeric glycogenin,
which was demonstrated by other authors, is not the unique reaction
mechanism for the intramolecular glucosylation of its tyrosine
residue. In the present work we analyzed whether in the dimer the
glycogenin subunit is able to carry out the glucosylation by both,
intersubunit and intrasubunit reactions. This study was accomplished
using non-glucosylated apo-glycogenin (Gn) and measuring the specific
autoglucosylation rate (SAR) of both, the monomer, and the monomer
forced to dimerize by mixing with the proper amount of a) Gn mutant
having intact glucosilable tyrosine but lacking activity (sGn), or b)
a double mutant lacking activity and the substrate tyrosine residue
(nGn). We have also analyzed whether any difference existed between
monomeric and dimeric glycogenin in the polymerization degree of the
linked oligoglucan acquired by full autoglucosylation. The study was
carried out by measuring the specific autoglucosylation extent (SAE)
of Gn monomer and dimer and of the mixtures of wild type and mutant
enzymes above mentioned. The described results are discussed in terms
of regulation at the initial step of the de
novo
glycogen biosynthesis by the glycogenin capacity to display two
different reaction mechanisms, and to acquire different
autoglucosylation degree.