Abstract: 3-HP is an excellent chemical intermediate，and the study on the production of 3-HP with glycerol as substrate is favored，while the main reason for limiting 3-HP production is the low activity of AldH. A gene of α-ketoglutorate semialdehye dehydrogenase（KGSADH）from Azospirillam brasilense was constructed by homology modeling and structure analysis. The KGSADH with high activity was obtained by site-directed mutation. The KGSADH was expressed and purified for the investigation of enzymatic properties. The results revealed that the activity of TU-KGSADH（E120D / P219A）reached 6.03 U/mg，which was 322% higher than that of the original KGSADH. The optimal temperature of TU-KGSADH decreased from 35℃ to 30℃，the thermostability reduced，and the optimal pH was 8.0 and enzymatic activity was improved slightly under pH 6.0-8.0. Zn²⁺ had a strong inhibitory effect on the activity of KGSADH，while Co²⁺，Fe³⁺ and Fe²⁺ had a great effect on the activity of KGSADH. In the kinetic aspect of the TU-KGSADH，the Km with acetaldehyde as a substrate reduced from 7.58 to 6.28 mmol/L，and Vmax increased from 10.6 to 12.3 U/mg. Finally，the factors affecting the changes of enzymatic properties were analyzed，The 120 site mutation was associated with the decrease of the optimal pH and pH stability to acidic migration，and the 219 site mutation may be the reason for the decrease of the optimum temperature and thermal stability，providing a fine reference for further research in directional modification of aldehye dehydrogenase.

Key words: α-ketoglutorate semialdehye dehydrogenase, site-directed mutation, expression and purification, enzymatic properties