Pseudomonas putida SJTE-1 can utilize 17 beta-estradiol (E2) as its carbon source, while the enzymes for E2 transformation in this strain is still unclear. 17 beta-hydroxysteroid dehydrogenases (17 beta-HSD) can catalyze the reduction/oxidation at C-17 site of steroid hormone specifically, critical for steroid transformation. Here a novel 3-oxoacyl-(acyl-carrier protein) (ACP) reductase (ANI02794.1) was identified as it could b beta-estradiol, and was proved to be capable of functioning as 17 beta-HSD. Sequences alignment showed it contained the two consensus regions and the conserved residues of short-chain dehydrogenase/reductase (SDR). Its encoding gene was cloned and over-expressed in Escherichia coli BL21(DE3) strain, and the recombinant protein was purified by the metal-ion affinity chromatography with the yield of 18 mg/L culture. HPLC (High Performance Liquid Chromatography) detection showed this enzyme could convert 17 beta-estradiol into estrone using NAD(+) as cofactor. Its K-m value was 0.082 mM and its V-max value was 0.81 mM/s; its transformation efficiency of 17 beta-estradiol into estrone was over 96.6% in five minutes. Its optimal temperature was 37 degrees C and optimal was pH 9.0; the divalent ions had different effects on the enzymatic activity. In conclusion, this 3-oxoacyl-ACP reductase functioned as 17 beta-HSD in P. putida SJTE-1 and played important role in its estrogen metabolism. (C) 2018 Elsevier Inc. All rights reserved.