Abstract: SOD gene was cloned from Nostoc flagelliforme and the amino acid sequence is 97% identical to that of Nostoc commune published. The gene was inserted into a constructed E.coli expression plasmid pET-sod and the plasmid was transferred into expressing host BL21. Induced by 1 mmol·L^-1 IPTG,the recombinant SOD of Nostoc flagelliforme was accumulated to a very high percent and the protein is exist as soluble protein. SDS-PAGE analysis revealed that the molecular weight of expression SOD of Nostoc flagelliforme was approximate 22 kd. Purified by Ni²⁺-resin column,the specific enzymatic activity was measured using NBT method and the calculated result of this purified enzyme is 2 550 U·mg^-1. It was also found that after high temperature stress at 60℃ for 90 min,the specific enzymatic activity still retains 85%.

Key words: Nostoc flagelliforme, gene cloning of SOD, induced expression, activity measurement of SOD