Engineered 3-Ketosteroid 9a-Hydroxylases in Mycobacterium neoaurum: an Efficient Platform for Production of Steroid Drugs

3-Ketosteroid 9α-hydroxylase (Ksh) consists of a terminal oxygenase (KshA) and a ferredoxin reductase and is indispensable in the cleavage of steroid nucleus in microorganisms. The activities of Kshs are crucial factors in determining the yield and distribution of products in the biotechnological tr...

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Bibliographic Details
Published in:Applied and environmental microbiology 2018-07, Vol.84 (14), p.e02777-17
Main Authors: Liu, Hao-Hao, Xu, Li-Qin, Yao, Kang, Xiong, Liang-Bin, Tao, Xin-Yi, Liu, Min, Wang, Feng-Qing, Wei, Dong-Zhi
Format: Article
Language:English
Subjects:
Androst-16-en-3-one
Androstenedione
Biotechnology
Catabolism
Cholesterol
Ferredoxin
Ferredoxin reductase
Genetic engineering
Genetic transformation
Homology
Hydroxylase
Industrial applications
Metabolism
Microorganisms
Mutation
Mycobacterium neoaurum
Nuclei
Oxygenase
Phytosterols
Steroids
Sterols
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Summary:3-Ketosteroid 9α-hydroxylase (Ksh) consists of a terminal oxygenase (KshA) and a ferredoxin reductase and is indispensable in the cleavage of steroid nucleus in microorganisms. The activities of Kshs are crucial factors in determining the yield and distribution of products in the biotechnological transformation of sterols in industrial applications. In this study, two KshA homologues, KshA1N and KshA2N, were characterized and further engineered in a sterol-digesting strain, Mycobacterium neoaurum ATCC 25795, to construct androstenone-producing strains. kshA1N is a member of the gene cluster encoding sterol catabolism enzymes, and its transcription exhibited a 4.7-fold increase under cholesterol induction. Furthermore, null mutation of kshA1N led to the stable accumulation of androst-4-ene-3,17-dione (AD) and androst-1,4-diene-3,17-dione (ADD). We determined kshA2N to be a redundant form of kshA1N. Through a combined modification of kshA1N, kshA2N, and other key genes involved in the metabolism of sterols, we constructed a high-yield ADD-producing strain that could produce 9.36 g liter−1 ADD from the transformation of 20 g liter−1 phytosterols in 168 h. Moreover, we improved a previously established 9α-hydroxy-AD-producing strain via the overexpression of a mutant KshA1N that had enhanced Ksh activity. Genetic engineering allowed the new strain to produce 11.7 g liter−1 9α-hydroxy-4-androstene-3,17-dione (9-OHAD) from the transformation of 20.0 g liter−1 phytosterol in 120 h.
ISSN:0099-2240
1098-5336
DOI:10.1128/AEM.02777-17