Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1991743 | The Journal of Steroid Biochemistry and Molecular Biology | 2012 | 11 Pages |
Steroid degradation by Comamonas testosteroni and Nocardia restrictus have been intensively studied for the purpose of obtaining materials for steroid drug synthesis. C. testosteroni degrades side chains and converts single/double bonds of certain steroid compounds to produce androsta-1,4-diene 3,17-dione or the derivative. Following 9α-hydroxylation leads to aromatization of the A-ring accompanied by cleavage of the B-ring, and aromatized A-ring is hydroxylated at C-4 position, cleaved at Δ4 by meta-cleavage, and divided into 2-hydroxyhexa-2,4-dienoic acid (A-ring) and 9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid (B,C,D-ring) by hydrolysis. Reactions and the genes involved in the cleavage and the following degradation of the A-ring are similar to those for bacterial biphenyl degradation, and 9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid degradation is suggested to be mainly β-oxidation. Genes involved in A-ring aromatization and degradation form a gene cluster, and the genes involved in β-oxidation of 9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid also comprise a large cluster of more than 10 genes. The DNA region between these two main steroid degradation gene clusters contain 3α-hydroxysteroid dehydrogenase gene, Δ5,3-ketosteroid isomerase gene, genes for inversion of an α-oriented-hydroxyl group to a β-oriented-hydroxyl group at C-12 position of cholic acid, and genes possibly involved in the degradation of a side chain at C-17 position of cholic acid, indicating this DNA region of more than 100 kb to be a steroid degradation gene hot spot of C. testosteroni.Article from a special issue on steroids and microorganisms.
Research highlights► C. testosteroni degrades steroids via aromatization of the A-ring, being degraded like biphenyl. ► B,C,D-rings and side chain at C-17 of cholic acid are degraded mainly by β-oxidation. ► The degradation genes make two gene clusters with 3α-dehydrogenase and isomerase between them. ► The c.a 100 kb DNA region containing these genes may be a steroid degradation gene hot spot. ► Several genera of bacteria have putative steroid degradation genes with high similarity.