Analysis of granule-associated Starch branching enzyme IIb, involved in amylose extender mutation of maize

Abstract

Maize starch is an important industrial commodity. Starch synthase, phosphorylase, branching and debranching enzymes act in concert and results in a particular starch architecture. Starch branching enzymes play an important role in defining the overall starch structure. In maize endosperm, Starch branching enzyme IIb is predominant. The computational structure of Starch branching enzyme IIb has been determined. The putative substrate binding site and active site pore channel have been elucidated. As the enzyme is known to prefer amylopectin as substrate, the disachharide melibiose containing α- 1,6 glycosidic bond was docked on the modelled protein. The substrate binding site and active site channel has been discussed. Understanding of starch structure is essential for its modification and processing in forms, that are desirable for specific end-use applications. Generation of feedstock specific for a particular starch modification would result in environmentally-friendly starch production system by minimizing the requirement of chemicals for starch modifications. This is also necessary for allele mining to direct further breeding goals in this area.