The scientist of the Joint Laboratory of Biotechnology and Enzyme Catalysis have shown that 3-ketosteroid Δ1-dehydrogenases exhibit the universal capability to dehydrogenase 17-substituted 3-ketosteroids. This feature was previously attributed only to several unique enzymes from organisms metabolizing cholesterol (such as Sterolibacterium denitrificans). The discovery was published in Microbial Cell Factories.
The story of this discovery started with theoretical modeling and NCN-funded project “The mechanism of regioselective oxidative dehydrogenation of3-ketosteroids catalyzed by Δ1-cholest-4-en-3-one dehydrogenase from Sterolibacterium denitrificans”. We observed that extended 3-ketosteroids docked to the only know at that time structure of KSTD enzyme from Rhodococcus erythropolis are bound only with the steroid ring system. The C17 substituent was protruding out of the enzyme to the solvent. Based on this observation we formed the hypothesis that such substrate can be converted also by KSTD from R. erythropolis and not only by AcmB from S. denitrificans. This hypothesis was challenging the experimental evidence reported previously in the literature by scientists from the University of Groningen.
With help of Dr. Ali Rohman from the University of Groningen, Netherlands and the Universitas Airlangga, Indonesia who studied the enzyme for many years, we tested its activity under the same conditions as AcmB i.e., in the presence of cyclodextrin solubilizer which increases the bioavailability of the hydrophobic steroids. Although KSTD from R. erythropolis still exhibited a higher affinity for smaller ketosteroids, like androsterone or testosterone, it was able to efficiently convert cholest-4-en-3-one or even 3-ketosaponin – diosgenone.
As a consequence of this discovery, it will be possible to extend the substrate scope of KSTD enzymes which are currently industrially employed for the dehydrogenation of various important pharmaceuticals.