Mechanisms of monomeric and dimeric glycogenin autoglucosylation

FEDERICO M. ISSOGLIO; MARÍA E. CARRIZO; JORGE M. ROMERO; JUAN A. CURTINO

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Lugar: Baltimore; Año: 2012 vol. 287 p. 1955 - 1955

nitiation of glucose polymerization by glycogenin autoglucosylation at Tyr-194 is required to prime de novo biosynthesis of glycogen. It has been proposed that the synthesis of the primer proceeds by intersubunit glucosylation of dimeric glycogenin, even though it has not been demonstrated that this mechanism is responsible for the described polymerization extent of 12 glucoses produced by the dimer. We reported previously the intramonomer glucosylation capability of glycogenin without determining the extent of autoglucopolymerization. Here, we show that the maximum specific autoglucosylation extent (MSAE) produced by the non-glucosylated glycogenin monomer is 13.3 ± 1.9 glucose units, similar to the 12.5 ± 1.4 glucose units measured for the dimer. The mechanism and capacity of the dimeric enzyme to carry out full glucopolymerization were