Expression, immobilization and enzymatic properties of glutamate decarboxylase fused to a cellulose-binding domain

Abstract

Escherichia coli-derived glutamate decarboxylase (GAD), an enzyme that catalyzes the conversion of glutamic acid to gamma-aminobutyric acid (GABA), was fused to the cellulose-binding domain (CBD) and a linker of Trichoderma harzianum endoglucanase II. To prevent proteolysis of the fusion protein, the native linker was replaced with a S3N10 peptide known to be completely resistant to E. coli endopeptidase. The CBD-GAD expressed in E. coli was successfully immobilized on Avicel, a crystalline cellulose, with binding capacity of 33 ± 2 nmolCBD-GAD/gAvicel and the immobilized enzymes retained 60% of their initial activities after 10 uses. The results of this report provide a feasible alternative to produce GABA using immobilized GAD through fusion to CBD. © 2012 by the authors; licensee MDPI, Basel, Switzerland.