RAPID DETERMINATION OF GLUTAMATE DECARBOXYLASE ACTIVITY FROM LACTIC ACID BACTERIA BY SPECTROMETRIC METHOD AND ITS APPLICATIONS / 微生物学通报

ABSTRACT

In this paper, a colorimetric method with high sensitivity, reproducibility and low cost for determining glutamate decarboxylase (GAD) activity was developed based on Berthelot reaction. The optimum substrate system is 0.2 mol/L MacIlvaine buffer pH4.7, containing 0.1 mmol/L pyridoxal phosphate (PLP) and 10 mmol/L L-monosodium glutamate (L-MSG). The reaction mixture consisted of 200 ?L substrate solution and 1～100 ?L enzyme preparation from lactic acid bacteria and was incubated at 30℃. The enzymatic reaction was terminated by immersion in ice-water and addition of 200 ?L 0.2 mol/L sodium borate buffer, pH9.0, then 1 mL 6% phenol solution and 400 ?L sodium hypochloride were added. Color development was carried out in boiling water for 10 min then immediately put in ice-water bath for 20 min. The optical density is read at 630 nm. ?-aminobutyric acid (GABA) produced was calculated using the standard curve. Applications of the method in GAD studies were discussed.