INVESTIGADORES
ROMERO jorge Miguel
congresos y reuniones científicas
Título:
The auto-glucopolymerization extent of monomeric and dimeric glycogenin
Autor/es:
ISSOGLIO, FEDERICO M.; CARRIZO, MARÍA E.; ROMERO, JORGE M; CURTINO, J.A.
Lugar:
Puerto Madryn
Reunión:
Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2010
Institución organizadora:
Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)
Resumen:
The formation of glycogenin
(Gn)-bound a-1,4-oligoglucan
primer
is required for the de
novo biosynthesis of
glycogen (G). Dimeric
Gn, as it exists in solution and in
the enzyme crystals, was
considered to be the molecular form
which synthesizes the primer by
intersubunit glucosylation
mechanism. We have described however
that monomeric Gn is also able to
catalyze its intramolecular
glucopolymerization. In considering
which Gn form actually primes
G biosynthesis, this might be determined
by the polymerization
degree (pd) of the Tyr-linked
oligoglucan the Gn form can produce,
having the size required by glycogen
synthase and branching
enzyme for further elongation and
branching. A pd of 12 was
reported for the oligoglucan produced
by Gn dimer; however the
auto-glucopolymerization extent
capacity of the monomer was
unknown. Now we determined the
glucopolymerization degree of
fully autoglucosylated monomeric and
homodimeric Gn and of
heterodimers formed by mixing 1) a
Gn mutant lacking its tyrosine
acceptor with a mutant containing
the tyrosine acceptor but lacking
glucosylation activity, and 2) the
wild type enzyme with a mutant
which lacked both, glucosylating
activity and tyrosine acceptor. The
results show that besides the intersubunit
glucosylation of Gn dimer,
the intramolecular glucosylation of
Gn monomer can produce the
oligo-glucopolymer
primer for G biosynthesis.