A Saliva-Inspired Model of Enzymatic Starch Hydrolysis by Alpha Amylase

We demonstrate that the enzymatic activity of alpha-amylase (AA) can serve as an effective physicochemical trigger for membrane remodeling in giant unilamellar vesicles (GUVs). This work provides insight into how primitive protocellular reactions directly translate into the membrane's mechanical responses. Analysis of the potato starch utilized in this work is composed of ~26\% amylose and ~75\% amylopectin. Quantitative DNS analysis revealed time- and concentration-dependent accumulation of reducing sugars during starch degradation by AA. The HPLC-RID chromatograms demonstrated the synthesis of glucose, maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose, and maltoheptaose, with maltose and maltotriose as the major products. The accumulation of these soluble hydrolysis products gradually increases the osmolarity of the extracellular medium surrounding the vesicles, leading to osmotic asymmetry across the membrane. This biochemical framework provides a quantitative basis for understanding membrane deformation, curvature generation, vesicle deflation, and budding. In addition to the specific starch--$\alpha$-amylase system studied here, our work uncovers a general mechanism by which external biochemical reactions control membrane shape transformations via osmotic coupling. Such enzyme-driven remodeling offers a simple yet powerful strategy for inducing dynamic structural changes in artificial cells. It may provide insight into primitive protocellular processes in which metabolic activity and membrane mechanics were inherently coupled.