Recombinant expression and preliminary characterization of the Human Glycogen Branching Enzyme

ISSOGLIO, FEDERICO M.; CARRIZO, MARÍA E.; CURTINO, JUAN A.

Mendoza

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación Bioquimíca y Biología Molecular (SAIB); 2012

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)

Glucose is the principal source of energy for most cells. In mammals, glucose is stored as glycogen, the branched polymer formed by linear alpha-1,4 oligoglucan chains linked by alpha-1,6-glucosidic bonds. Three enzymes are mainly responsible for the de novo biosynthesis of glycogen. First, glycogenin autoglucosylation produces a protein-bound oligoglucan that serves as a primer for the other two enzymes, then glycogen synthase elongates the chains, and the glycogen branching enzyme catalyzes the cleavage of a linear segment and transfers this chain to the 6-position of a non-terminal glucosyl unit. Glycogen branching enzyme (GBE) is the least studied of the three enzymes. It has been isolated and characterized in some bacteria, rabbit and rat. The human enzyme has been mainly studied in clinical cases of glycogen storage disease type IV caused by deficiencies in GBE. Phosphoproteome and acetylome analysis over human cell lines suggests the possibility of a regulation for branching activity in humans by phosphorylation on tyrosine 173 and acetylation on lysine 68. In this study we report the recombinant production of human glycogen branching enzyme in Pichia pastoris, and in insect cells using the baculovirus expression system, and the activity analysis of the recombinant enzymes produced in the two expression systems.