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

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

Córdoba

Congreso; LII Reunión de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2016

SAIB

 Starch branching enzyme (BE) is a highly conservedprotein from plants to algae. This enzyme participates on starch granuleassembly 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, thefinal structure of the starch granule. In this work we describe the function ofa starch branching enzyme from the picoalgae Ostreococcus tauri. Although previous in silico evidence suggested that this protein is a StarchDebranching Enzyme, structure-function studies confirmed that this BEcomprising two in tandem carbohydrate binding domains (from CBM41 and CBM48families) at the N-terminal end of the protein followed by a C-terminalcatalytic domain. The analysis of truncated isoforms show that the CBMs binddifferentially to starch and the distinct starch fractions. Moreover, nocatalytic activity was detected in the CD alone or with the truncated forms ofthe protein. The results suggest that this O.tauri protein is a functional BE containing a CBM41 and CBM48 that areessential for enzyme activity and regulation.