earticle

영어

Glutamate decarboxylase (GAD : EC 4.1.1.15) is a pyridoxal 5’- phosphate (PLP) dependent enzyme, which catalyses the α- decarboxylation of L-glutamate to produce γ-aminobutyrate (GABA). GADB from E. coli is multimeric structure (hexamer) and its N-terminal residues 1-15 form the triple helix bundle at acidic pH. In this study, we showed that the thermostability depends on the structure of N-terminal changed by pH. And the thermostability of GADB was improved through N-terminal residues protein engineering. Eight mutants located at near N-terminal of GAD were designed considering the ionic interaction and hydrophobic interaction between the N-terminal α-helix residues. The GADB-WT and its N-terminal mutants were expressed successfully in E. coli expression host. The thermostability was determined by T50 10 value. The T50 10 value is the temperature at which 50% of initial enzymatic activity remains after 10 min heat treatment. The T50 10 of mutants were increased compared to that of GADB-WT. Additionally, the double mutant of N-terminal residues showed synergy effect on the thermostability.