A Model of Amylopectin Biosynthesis based on the Activities of Key Enzymes Coupled with the Crystallization Process

Amylopectin is the major glucose polymer in the plant starch granule. The amylopectin molecules have a highly ordered structure of alternating regions between the crystalline and amorphous lamellae, which is distinct from glycogen (the principle form of carbohydrate storage in bacteria and animals). Although several key enzymes involved in the amylopectin biosynthesis have been studied extensively, the underlying mechanism that gives rise to the unique structure of amylopectin remains largely unknown. In the present work, the Monte Carlo simulation technique is used to study the roles of the key enzymes and their relationship in the biosynthesis of amylopectin. We propose a mechanism of the amylopectin biosynthesis based on the activities of the key enzymes coupled with the crystallization process. The proposed mechanism can explain the characteristics of the molecular weight distributions of the molecules and how the amylopectin structure arises.