Both the formation and degradation of amylopectin is important to the metabolic processes of organisms. Amylopectin is one of the two dominant components of starch, and starch is a successful storage molecule for energy. Because of this, it is synthesized and broken down in most plants and cyanobacteria. In fact, amylopectin seems to rival glycogen, the energy storage molecule in animals, because it is able to store more glucose units and henceforth more energy.
The synthesis of amylopectin depends on the combined efforts of four different enzymes. These four different enzymes are:
# ADP glucose pyrophosphorylase (AGPase)
# soluble starch synthase (SS)
# starch branching enzyme (BE)
# starch debranching enzyme (DBE)
Amylopectin is synthesized by the linkage of α(1→4) Glycosidic bonds. The extensive branching of amylopectin (α(1→6) Glycosidic bond) is initiated by BE and this is what differentiates amylose from amylopectin. DBE is also needed during this synthesis process to regulate the distribution of these branches.
The breakdown of amylopectin has been studied in context with the breakdown of starch in animals and humans. Starch is mostly composed of amylopectin and amylose, but amylopectin has been shown to degrade more easily. The reason is most likely because amylopectin is highly branched and these branches are more available to digestive enzymes. In contrast, amylose tends to form helices and contain hydrogen bonding.
The breakdown of starch is dependent on three enzymes, among others:
# alpha, beta amylases
# phosphorylases
# starch debranching enzyme (DBE)
There are enzymes that are involved in the synthesis and degradation of amylopectin that have isoforms that display different relationships with proteins and other enzymes. For example, there are many versions of SS (Starch Synthase). Even the third isoform (SS-III) has two different versions. It is believed that SS-I and SS-II both have a role in elongating the chains of amylopectin branches. SS-IV is also thought to be responsible for the leaf-like structure of starch granule clusters.