Defining carbohydrate binding of glucan phosphatases via Affinity gel electrophoresis

In plants, starch is the energy storage molecule that is readily broken down when needed. In animals, glycogen is the molecule that is used for energy storage. Both molecules are comprised of α-1, 4 linked glucose polymer chains and α-1,6 glucose branches that are tightly compacted. Our lab has determined the x-ray crystal structures of both plant and human glucan phosphatases and their enzymatic mechanisms.

Despite this progress, we lacked the techniques to quickly and efficiently quantify their glucan phosphatase affinities for different substrates. The main objective of this study was to determine a technique to measure carbohydrate binding quickly and efficiently. We established a protocol to reproducibly and quantitatively measure the binding of the enzymes to glucans utilizing Affinity Gel Electrophoresis (AGE).

The results show that the various glucan phosphatases possess differing abilities to bind to different glucan substrates. The plant glucan phosphatase SEX4 possesses a 50 fold higher affinity for the glucan amylopectin than LSF2, while SEX4 only possessed a 3 fold higher affinity for the glucan amylose than LSF2.

Mutations were made to the various domains of the plant and animal glucan phosphatases to determine which regions of the enzyme are most necessary for binding. Footnotes This abstract is from the Experimental Biology 2016 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.