Rhodococcus strains as source for ene-reductase activity

Rhodococcus strains are ubiquitous in nature and known to metabolise a wide variety of compounds. At the same time, asymmetric reduction of C=C bonds is important in the production of high-valued chiral building blocks. In order to evaluate if Rhodococci can be used for this task, we have probed several Rhodococcus rhodochrous and R. erythropolis strains for ene-reductase activity. A series of substrates including activated ketones, an aldehyde, an imide and nitro-compound were screened using whole cells of seven Rhodococcus strains. This revealed that whole cells of all Rhodococcus strains showed apparent (S)-selectivity towards ketoisophorone, while most other organisms show (R)-selectivity for this compound. Three putative ene-reductases from R. rhodochrous ATCC 17895 were heterologously expressed in Escherichia coli. One protein was purified and its biocatalytic and biochemical properties were characterised, showing typical (enantioselective) properties for class 3 ene-reductases of the old yellow enzyme family.