Potato starch synthases: Functions and relationships

摘要

Starch, a very compact form of glucose units, is the most abundant form of storage polyglucan in nature. The starch synthesis pathway is among the central biochemical pathways, however, our understanding of this important pathway regarding genetic elements controlling this pathway, is still insufficient. Starch biosynthesis requires the action of several enzymes. Soluble starch synthases (SSs) are a group of key players in starch biosynthesis which have proven their impact on different aspects of the starch biosynthesis and functionalities. These enzymes have been studied in different plant species and organs in detail, however, there seem to be key differences among species regarding their contributions to the starch synthesis. In this review, we consider an update on various SSs with an emphasis on potato SSs as a model for storage organs. The genetics and regulatory mechanisms of potato starch synthases will be highlighted. Different aspects of various isoforms of SSs are also discussed. Highlights ? We have shown that transgenic plants with modified starches has been generated by manipulation of various SSs. ? A detailed characterization of the biosynthetic machinery is required to understand the effects of inhibiting any particular SSs. ? A comparison is made between the predicted 3D structure of potato SSs with those of rice, barley and glycogen synthases. ? We have pointed out the similarities and differences between different potato SSs. ? We have managed to summarize most of the finding regarding in planta modification of different SSs.