Cloning, expression and structural investigations of P5βR-like enone reductases from various

Abstract

5β-configured cardenolides are of great medicinal and economical importance in the treatment of cardiac insuffiency in humans. Considering their biosynthesis the stereospecific reduction of progesterone to 5β-pregane-3,20-dion is often referred to as key step, because here the characteristic cis configuration between ring A and B is formed. The reaction is catalysed by the enzyme progesterone 5β-reductase (P5βR), which has been cloned from several members of the genus Digitalis and functionally expressed in E. coli [1]. The crystal structure of Digitalis lanata P5βR has been solved revealing a novel class of short chain dehydrogenases/reductases (SDRs), with only two of the typical catalytic residues (K147 and Y179) being conserved [2]. An orthologous gene (VEP1) has also been cloned from Arabidopsis thaliana, which does not produce cardenolides. The respective recombinant enzyme was also capable of reducing progesterone stereoselectively [3]. Both enzymes were capable of reducing other steroidal, cyclic or noncyclic enone substrates [4].