Composition of Clusters and Building Blocks in Amylopectins from Maize Mutants Deficient in Starch Synthase III

摘要

Branches in amylopectin are distributed along the backbone. Units of the branches are building blocks (smaller) and clusters (larger) based on the distance between branches. In this study, composition of clusters and building blocks of amylopectins from dull1 maize mutants deficient in starch synthase HI (SSIII) with a common genetic background (W64A) were characterized and compared with the wild type. Clusters were produced from amylopectins by partial hydrolysis using α-amylase of Bacillus amylobquefaaens and were subsequently treated with phosphorylase α and β-amylase to produce φ, β-imii dextrins. Clusters were further extensively hydrolyzed vnth the "-amyIase to produce building blocks. Stmctures of clusters and building blocks were analyzed by diverse chromatographic techniques. The results showed that the dulll mutation resulted in larger clusters with more singly branched building blocks. The average cluster contained ~5.4 blocks in dulll mutants and ~4.2 blocks in the wild type. The results are compared with previous results from SSIII-deficient amol barley and suggest fundamental differences in the cluster structures.