Structures and molecular mechanisms of action of the cholesterol C17 side-chain-degrading enzymes

Kong, Kexin; Zhang, Min; Zhang, Hongmei; Zhang, Chengyu; Wang, Chunhua; Yan, Xiaohui

doi:10.1007/s43393-022-00083-x

Cited by 2 publications

(1 citation statement)

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“…To develop the strains for the production of C-19 and C-22 steroids, some key genes, including those encoding the ketosteroid-Δ 1 -dehydrogenases homologs (KstDs) and/or 3-ketosteroid-9α-hydroxylases homologs (KshAs), involved in steroid nucleus degradation need to be blocked [ 27 , 28 ]. Therefore, the degradation process of the C17 side chain of sterols is essential for the production of C-19 or C-22 metabolites [ 29 , 30 ]. The degradation of the C17 side chain is similar to the β-oxidative degradation of fatty acids, and the conversion process from sterols to C-19 steroids is known as the AD sub-pathway [ 31 , 32 ].…”

Section: Introductionmentioning

confidence: 99%

Unravelling and engineering an operon involved in the side-chain degradation of sterols in Mycolicibacterium neoaurum for the production of steroid synthons

Zhao

Liu

et al. 2023

Biotechnol Biofuels

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Background Harnessing engineered Mycolicibacteria to convert cheap phytosterols into valuable steroid synthons is a basic way in the industry for the production of steroid hormones. Thus, C-19 and C-22 steroids are the two main types of commercial synthons and the products of C17 side chain degradation of phytosterols. During the conversion process of sterols, C-19 and C-22 steroids are often produced together, although one may be the main product and the other a minor byproduct. This is a major drawback of the engineered Mycolicibacteria for industrial application, which could be attributed to the co-existence of androstene-4-ene-3,17-dione (AD) and 22-hydroxy-23,24-bisnorchol-4-ene-3-one (HBC) sub-pathways in the degradation of the sterol C17 side chain. Since the key mechanism underlying the HBC sub-pathway has not yet been clarified, the above shortcoming has not been resolved so far. Results The key gene involved in the putative HBC sub-pathway was excavated from the genome of M. neoaurum by comparative genomic analysis. Interestingly, an aldolase- encoding gene, atf1, was identified to be responsible for the first reaction of the HBC sub-pathway, and it exists as a conserved operon along with a DUF35-type gene chsH4, a reductase gene chsE6, and a transcriptional regulation gene kstR3 in the genome. Subsequently, atf1 and chsH4 were identified as the key genes involved in the HBC sub-pathway. Therefore, an updated strategy was proposed to develop engineered C-19 or C-22 steroid-producing strains by simultaneously modifying the AD and HBC sub-pathways. Taking the development of 4-HBC and 9-OHAD-producing strains as examples, the improved 4-HBC-producing strain achieved a 20.7 g/L production titer with a 92.5% molar yield and a 56.4% reduction in byproducts, and the improved 9-OHAD producing strain achieved a 19.87 g/L production titer with a 94.6% molar yield and a 43.7% reduction in byproduct production. Conclusions The excellent performances of these strains demonstrated that the primary operon involved in the HBC sub-pathway improves the industrial strains in the conversion of phytosterols to steroid synthons.

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