Steroid transformations by a strain of Arthrobacter oxydans incapable of steroid ring degradation

Arthrobacter oxydans 317 which is able to bring about the complete degradation of β‐sitosterol was treated with acridine orange to obtain a plasmid cured strain Arthrobacter 317AL, incapable of producing steroid ring degradation. The strain was neither able to form 4‐androstene‐3,17‐dione(AD) from β‐sitosterol nor to convert AD to 1,4‐androstadiene‐3,17‐dione(ADD). It was, however, able to hydroxylate AD and ADD at the C‐17 position to form testosterone and 1,4‐androstadiene‐17β‐ol‐3‐one respectively. The strain could grow on β‐sitosterol presumably utilizing the degradation products of the sterol side chain. Partial degradation of the β‐sitosterol side chain was demonstrated by the isolation of 27‐norcholest‐4‐en‐3,24‐dione, a metabolic product of the side chain degradation. The existence of metabolic blocks in a further degradation of the side chain to AD, in 1,2‐dehydrogenation and 9α‐hydroxylation of the steroid ring structure was postulated.