Publication: Further Studies on the 3-Ketosteroid 9α-Hydroxylase of Rhodococcus ruber Chol-4, a Rieske Oxygenase of the Steroid Degradation Pathway
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2021-05-29
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Abstract
The biochemistry and genetics of the bacterial steroid catabolism have been extensively studied during the last years and their findings have been essential to the development of biotechnological applications. For instance, metabolic engineering of the steroid-eater strains has allowed to obtain intermediaries of industrial value. However, there are still some drawbacks that must be overcome, such as the redundancy of the steroid catabolism genes in the genome and a better knowledge of its genetic regulation. KshABs and KstDs are key enzymes involved in the aerobic breakage of the steroid nucleus. Rhodococcus ruber Chol-4 contains three kshAs genes, a single kshB gene and three kstDs genes within its genome. In the present work, the growth of R. ruber ΔkshA strains was evaluated on different steroids substrates; the promoter regions of these genes were analyzed; and their expression was followed by qRT-PCR in both wild type and ksh mutants. Additionally, the transcription level of the kstDs genes was studied in the ksh mutants. The results show that KshA2B and KshA1B are involved in AD metabolism, while KshA3B and KshA1B contribute to the cholesterol metabolism in R. ruber. In the kshA single mutants, expression of the remaining kshA and kstD genes is re-organized to survive on the steroid substrate. These data give insight into the fine regulation of steroid genes when several isoforms are present.
Los genomas de actinobacterias presentan una notable redundancia génica que les permite una gran versatilidad metabólica. En este trabajo se ha estudiado la expresión de los genes de enzimas relacionadas con el catabolismo de los esteroides, en concreto de las que son responsables de la ruptura inicial del anillo. Existen tres isoformas para la actividad Ksh y otras tres para la actividad KstD. Cuando una de ellas no está presente, la expresión de los demás genes se reorganiza para compensar el sistema.
Los genomas de actinobacterias presentan una notable redundancia génica que les permite una gran versatilidad metabólica. En este trabajo se ha estudiado la expresión de los genes de enzimas relacionadas con el catabolismo de los esteroides, en concreto de las que son responsables de la ruptura inicial del anillo. Existen tres isoformas para la actividad Ksh y otras tres para la actividad KstD. Cuando una de ellas no está presente, la expresión de los demás genes se reorganiza para compensar el sistema.