Avances en el estudio de las enzimas implicadas en la ruta de degradación del anillo esteroideo de "Rhodococcus ruber Chol-4"

Resum

Rhodococcus ruber strain Chol-4 is an actinobacteria isolated from a sewage sludge sample. It is able to grow in minimal medium supplemented with steroids and aromatic compounds, showing a large catabolic capacity. The degradation of aromatic compounds and steroids helps to maintain the global carbon cycle, and it also has an increasing number of biotechnological applications from biodegradation of pollutants to production of pharmaceutical compounds. The genus rhodococci contains multiple homologues of catabolic genes, which may be the reason of their wide and versatile catabolic capabilities. However, the redundancy of genes in the actinobacterial genomes results in a serious complication for metabolic engineering to obtain intermediates of industrial interest. The 3-ketosteroid-Δ1-deydrogenase activity (KstD) is a key enzyme in the general scheme of the bacterial steroid catabolism in combination with the 3-Ketosteroid-9α-Hydroxylase (KshAB), being both responsible of the steroid nucleus (rings A/B) breakage. KshAB initiates the opening of the steroid ring by the 9α-hydroxylation of the C9 carbon of 4-ene-3-oxosteroids (e.g. AD) or 1,4-diene-3-oxosteroids (e.g. ADD), transforming them into 9α-hydroxy-4-androsten-3,17-dione (9OHAD) or 9α-hydroxy-1,4-androstadiene-3,17-dione (9OHADD) respectively. KstD converts 4-ene-3-oxosteroids (e.g. AD) or 9-hydroxy-4-ene-3-oxosteroids (9OH-AD) to 1,4-diene-3-oxosteroids (e.g. ADD) or 9-hydroxy-1,4-diene-3-oxosteroids (e.g. 9OH-ADD) by trans-axial elimination of the C-1(α) and C-2(β) hydrogen atoms...