RESUMO
To improve 3-ketosteroid-△1-dehydrogenase(KSDH) activity and the transformation level for androst-4-ene-3,17-dione, 3-ketosteroid-△1-dehydrogenase gene(ksdD) from Arthrobacter simplex was cloned into plasmid pWB980 and expressed in B. subtilis WB600 under the control of promoter P43. The molecular weight of expressed enzyme was about 55kDa by SDS-PAGE analysis. The activitities assayed by spectrophotometrical method of intracellular and extracellular soluble enzyme were 110?0.5mU and 15?0.6mU per milligram of protein respectively. The transformation rate of androst-4-ene-3,17-dione by the B. subtilis recombinant cells was 45.3%. Compared with Arthrobacter simplex, the enzyme activity of KSDH expressed in B. subtilis was improved about 30 fold, and the transformation level of androst-4-ene-3,17-dione by the B. subtilis recombinant cells was improved about 10 fold. The recombinant B. subtilis cells used in biotransformation of steroids provided a new way for steroid medicines production.