Pyridoxine Supplementation Improves the Activity of Recombinant Glutamate Decarboxylase and the Enzymatic Production of Gama-Aminobutyric Acid

PLoS One. 2016 Jul 20;11(7):e0157466. doi: 10.1371/journal.pone.0157466. eCollection 2016.

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.

MeSH terms

  • Dietary Supplements*
  • Escherichia coli K12 / enzymology*
  • Fermentation
  • Gene Expression Regulation, Enzymologic
  • Glutamate Decarboxylase / genetics*
  • Glutamate Decarboxylase / metabolism
  • Pyridoxine / pharmacology
  • gamma-Aminobutyric Acid / biosynthesis*
  • gamma-Aminobutyric Acid / genetics

Substances

  • gamma-Aminobutyric Acid
  • Glutamate Decarboxylase
  • Pyridoxine

Grant support

This work received financial support from the National Science Fund for Distinguished Young Scholars (No.31425020), received by Jing Wu and the 111 Project (No. 111-2-06), received by Jing Wu.