Microbial Modifications of Androstane and Androstene Steroids by Penicillium vinaceum

The biotransformation of steroid compounds is a promising, environmentally friendly route to new pharmaceuticals and hormones. One of the reaction types common in the metabolic fate of steroids is Baeyer-Villiger oxidation, which in the case of cyclic ketones, such as steroids, leads to lactones. Fungal enzymes catalyzing this reaction, Baeyer-Villiger monooxygenases (BVMOs), have been shown to possess broad substrate scope, selectivity, and catalytic performance competitive to chemical oxidation, being far more environmentally green. This study covers the biotransformation of a series of androstane steroids (epiandrosterone and androsterone) and androstene steroids (progesterone, pregnenolone, dehydroepiandrosterone, androstenedione, 19-OH-androstenedione, testosterone, and 19-nortestosterone) by the cultures of filamentous fungus Penicillium vinaceum AM110. The transformation was monitored by GC and the resulting products were identified on the basis of chromatographic and spectral data. The investigated fungus carries out effective Baeyer-Villiger oxidation of the substrates. Interestingly, introduction of the 19-OH group into androstenedione skeleton has significant inhibitory effect on the BVMO activity, as the 10-day transformation leaves half of the 19-OH-androstenedione unreacted. The metabolic fate of epiandrosterone and androsterone, the only 5α-saturated substrates among the investigated compounds, is more complicated. The transformation of these two substrates combined with time course monitoring revealed that each substrate is converted into three products, corresponding to oxidation at C-3 and C-17, with different time profiles and yields.