Abstract
Mycobacteria are able to degrade natural sterols and use them as a source of carbon and energy. Several genes which play an important role in cholesterol ring degradation have been described in Mycobacterium smegmatis. However, there are limited data describing the molecular mechanism of the aliphatic side chain degradation by Mycobacterium spp. In this paper, we analyzed the role of the echA19 and fadD19 genes in the degradation process of the side chain of cholesterol and β-sitosterol. We demonstrated that the M. smegmatis fadD19 and echA19 genes are not essential for viability. FadD19 is required in the initial step of the biodegradation of C-24 branched sterol side chains in Mycobacterium smegmatis mc2155, but not those carrying a straight chain like cholesterol. Additionally, we have shown that echA19 is not essential in the degradation of either substrate. This is the first report, to our knowledge, on the molecular characterization of the genes playing an essential role in C-24 branched side chain sterol degradation in M. smegmatis mc2155.
Highlights
Fast-growing mycobacteria (M. smegmatis, M. vaccae, M. phlei, M. fortuitum) have been the subject of biotechnological research for many years
We have demonstrated that fadD19 is required in the initial step of biodegradation of C-24 demonstrated that fadD19 is required in the initial step of biodegradation of C-24 branched sterols in M. smegmatis
To confirm the essential role of FadD19 in the early step of β-sitosterol degradation, a complemented mutant was constructed carrying an intact fadD19 under control of its natural complemented mutant was constructed carrying an intact fadD19 under control of its natural putative putative promoter (M. smegmatis ∆fadD19; attB::PfadD19fadD19)
Summary
Fast-growing mycobacteria (M. smegmatis, M. vaccae, M. phlei, M. fortuitum) have been the subject of biotechnological research for many years. Molecular characterization studies concerning sterol degradation processes could be important for the biotechnological production of steroid drugs, and help widen our knowledge on the pathogenesis of Mycobacterium tuberculosis (Mtb). Several genes have been described in Mycobacterium smegmatis mc 155 which play an important role in cholesterol ring degradation. Ruprecht and co-workers showed that FadE34 ( known as ChsE3) in M. tuberculosis and CasC in R. jostii RHA1 catalyze the dehydrogenation of 5 C, but not 3 CoA ester substituents at ring D This observation proves that ACADs metabolize the steroid side chain and have separate chain length specificities [33]. In this paper we analyzed the role of selected M. smegmatis genes coding for enzymes engaged in in the process of degradation of the side chains of cholesterol and β-sitosterol (Scheme 1). Containing containing analyzed analyzed metabolites metabolites [14,24,25,35,37]
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