Identification and characterization of a novel starch branching enzyme from Ostreococcus tauri

DIEGO FABIAN GOMEZ CASATI; BARCHIESI, J; HEDIN, N; BUSI, M. V.

Cordoba

Congreso; LII Congreso Anual de la Sociedad Argentina de Investigación Bioquímica; 2016

Starch branching enzyme (BE) is a highly conserved protein from plants to algae. This enzyme participates on starch granule assembly by the addition of α-1,6 glucan branches in the α-1,4 polyglucans. This modification determines the fine structure of amylopectin, and thus, the final structure of the starch granule. In this work we describe the function of a gene coding for a starch branching enzyme from the picoalgae Ostreococcus tauri. Although in silico evidence suggested that this gene codes for a Starch Debranching Enzyme, structure-function studies confirmed that this gene encodes a BE comprising two in tandem carbohydrate binding domains (from CBM41 and CBM48 families) at the N-terminal end of the protein followed by a C-terminal catalytic domain. The analysis BE truncated isoforms show that the CBMs bind differentially to starch and the distinct starch fractions. Moreover, no catalytic activity was detected in the CD alone or with the truncated forms of the protein. The results suggest that the protein codified by this gene codifies for a functional BE containing a CBM41 and CBM48 that are essential for enzyme activity and regulation.