Inactivation and Thermal Stabilization of Glycogenin by Linked Glycogen

JORGE M ROMERO; MARIA E CARRIZO; GUILLERMO MONTICH; JUAN A CURTINO

Academic Press

Lugar: San Diego, CA; Año: 2001 vol. 289 p. 69 - 69

Glycogen-free but not glycogen-bound glycogenin transglucosylates dodecyl-beta-maltoside. Furthermore, its sugar nucleotide-binding site can be photoaffinity labeled using [beta-(32)P]5-azido-UDP-glucose. Disruption with DMSO of the hydrogen bonds that stabilize the alpha-helical structure of glycogen restored the photoaffinity labeling of the glycogen-bound enzyme but not its transglucosylation activity. The larger size polysaccharide that linked to glycogenin allowed transglucosylation corresponding to that of PG-200, a proteoglycogen species of M(r) 200 kDa. PG-200 showed lower activity and increased activation energy than glycogen-free glycogenin. Heat denaturation of glycogen-free and glycogen-bound glycogenin occurred at 51 and 64 degrees C, respectively. Active glycogenin was recovered after the glycogen-bound form was heated at 60-70 degrees C and immediately cooled. Treatment at 60 degrees C of the glycogen-free enzyme resulted in inactivation. This is the first report des