title: Pyridoxine Supplementation Improves the Activity of Recombinant Glutamate Decarboxylase and the Enzymatic Production of Gama-Aminobutyric Acid.
abstract: Glutamate decarboxylase (GAD) catalyzes the irreversible decarboxylation of L-glutamate to the valuable food supplement γ-aminobutyric acid (GABA). In this study, GAD from Escherichia coli K12, a pyridoxal phosphate (PLP)-dependent enzyme, was overexpressed in E. coli. The GAD produced in media supplemented with 0.05 mM soluble vitamin B6 analog pyridoxine hydrochloride (GAD-V) activity was 154.8 U mL-1, 1.8-fold higher than that of GAD obtained without supplementation (GAD-C). Purified GAD-V exhibited increased activity (193.4 U mg-1, 1.5-fold higher than that of GAD-C), superior thermostability (2.8-fold greater than that of GAD-C), and higher kcat/Km (1.6-fold higher than that of GAD-C). Under optimal conditions in reactions mixtures lacking added PLP, crude GAD-V converted 500 g L-1 monosodium glutamate (MSG) to GABA with a yield of 100%, and 750 g L-1 MSG with a yield of 88.7%. These results establish the utility of pyridoxine supplementation and lay the foundation for large-scale enzymatic production of GABA.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China.|School of Biotechnology and Key Laboratory of Industrial Biotechnology Ministry of Education, Jiangnan University, Wuxi, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China.|School of Biotechnology and Key Laboratory of Industrial Biotechnology Ministry of Education, Jiangnan University, Wuxi, China.
authors.forename: Lingqia
authors.initials: L
authors.lastname: Su
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China.|School of Biotechnology and Key Laboratory of Industrial Biotechnology Ministry of Education, Jiangnan University, Wuxi, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
mesh_terms: D019587:Dietary Supplements; D048168:Escherichia coli K12 / Q000201:enzymology*; D005285:Fermentation; D015971:Gene Expression Regulation, Enzymologic; D005968:Glutamate Decarboxylase / Q000235:genetics* / Q000378:metabolism; D011736:Pyridoxine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; D011736:Pyridoxine