Identifying Post‐translational Regulatory Strategies of Glucan Phosphatases in Transitory Starch Metabolism

Abstract

Plant glucan phosphatases remove phosphates from the outer most layers of the starch granule, which is already partially solubilized and phosphorylated by glucan dikinases. Thus, the activity of glucan phosphatase is at an interface between semi‐crystalline starch structure and soluble chains of amylopectin. Recent structural studies of glucan phosphatases bound to a soluble glucans have provided important insights into how glucan phosphatase family of enzymes engage with the linear portion of the amylopectin chains of the complex starch structure. However, our understanding of how these enzymes interact with the insoluble or partially soluble semi‐crystalline starch granule is not clear. Using enzymatic assays coupled with Differential Scanning Fluorometry (DSF) and X‐ray crystallographic studies, we have identified the physical mechanisms glucan phosphatases utilize to bind, activate and regulate their enzymatic activity at the starch granule. In this work, we also investigate how glucan phosphatases respond to the metabolic and energy changes during day and night. The findings explore novel posttranslational regulatory mechanisms of glucan phosphatase family of enzymes in transitory starch metabolism.