The Role of Pullulanase in Starch Biosynthesis, Structure, and Thermal Properties by Studying Sorghum with Increased Pullulanase Activity

Pullulanase is a starch debranching enzyme involved in starch biosynthesis, but its function in starch biosynthesis is not fully established. This study aims to understand its function by analyzing a sorghum variety ( SbPUL‐RA ) with increased pullulanase activity (67% higher than wild‐type). The results demonstrate that increased pullulanase activity has little or no effect on crystalline structure or amylose content; however, it increases the total amount of starch, and produces amylose with longer chains. The changed amylose structures results in slightly decreased starch gelatinization temperatures. These results indicate a hitherto unconsidered role for pullulanase during amylose biosynthesis: it removes shorter amylose branches, which further facilitate the elongation of existing amylose chains.