Improved substrate specificity for D-galactose of L-arabinose isomerase for industrial application |
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| Institution: | 1. The United Graduate School of Agricultural Sciences, Kagoshima University, 1-21-24, Korimoto, Kagoshima 890-0065, Japan;2. National Institutes for Quantum and Radiological Science and Technology, 2-4 Shirakata, Tokai, Ibaraki 319-1106, Japan;3. Research Center for Biotechnology, Indonesian Institute of Sciences (LIPI), Jalan Raya Bogor Km. 46, Cibinong 16911, Indonesia;1. State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, People''s Republic of China;2. International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, Jiangsu 214122, People''s Republic of China |
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| Abstract: | L-Arabinose isomerase isolated from Geobacillus stearothermophilus (GSAI) was modified to improve its substrate specificity for D-galactose for the production of D-tagatose, a potential reduced-energy sweetener. Among the selected residues, mutation at residue 18 produced a mutant strain, H18T, which exhibited increased activity for D-galactose compared with the wild-type (WT) enzyme. Analysis of the substrate specificity of H18T showed a 45.4% improvement for D-galactose. Replacing histidine with threonine at residue 18 resulted in approximately 2.7-fold and 1.8-fold higher substrate binding and catalytic efficiency, respectively, for D-galactose. Further enhancement of the specific activity and catalytic efficiency of H18T for D-galactose by up to 2.7-fold and 4.3-fold, respectively, was achieved by adding borate during L-arabinose isomerase catalysis. Moreover, H18T showed thermostability and no destabilization was detected, which is promising for the industrial production of D-tagatose. |
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