Abstract: This paper mainly studied the extraction,separation,analysis and structural characterization of gallic acid decarboxylase(GAD).The linear regression equation was established to determine GAD content by Coomassie brilliant blue method(Y=4.8748X-0.0255，R²=0.9922) and biuret colorimetry method(Y=0.2476X+0.0003，R²=0.9993).60% and 70% Ammonium sulfate was used to purify crude enzyme solution twice for 32 h with pH 6;then,35 kD dialysis membrane was used to filter the solution for 12-16 h;DEAE cellulose resin was applied to sequentially purify the solution and found the saturated adsorption amount of resin was 2.838 mg/g with the buffer of pH 6.5;G-100 Sephadex gel was selected to further purify enzyme extract in the present of 0.4 mol/L NaCl as the eluent.SDS-PAGE polyacrylamide gel electrophoresis was used to separate the protein and MALDI-TOF-MS was applied to analyze and identify its structure:the molecular weight was 45.62 kD,isoelectric point 5.19,matching to protein gi/334732950,it showed they had similar properties,but because matching rate was only 3%,hence it was supposed that GAD could be a new protein.

Key words: gallic acid decarboxylase, microbial degradation, pyrogallic acid, structural characterization