Biotransformation of steroids by the fission yeast Schizosaccharomyces pombe

The fungal biotransformation of steroids is of applied interest due to the economic importance of such stereo- and regiospecific reactions and also in the context of ergosterol pathway engineering to produce vitamin D and ste roidal products. In Schizosaccharomyces pombe no steroid hydroxylation as i s found in filamentous fungi was observed, but a cytosolic NAD(H)/NADP(H)-d ependent hydroxysteroid dehydrogenase activity was identified. Progesterone was reduced at the Delta(4) double bond (in vivo only) as well as at the C -3 and C-20 keto groups. Testosterone and 4-androsrene-3,17-dione were inte rconverted and 5 alpha-pregnane-3,20-dione and 5 beta-pregnane-3,20-dione w ere reduced to 3-hydroxy products. The reactions were sometimes reversible and showed regio- and stereo specificity. In S. pombe more than one steroid dehydrogenase homologue is likely to occur, as has been observed in Saccha romyces cerevisiae. Our findings indicate that genes encoding soluble prote ins should be examined as candidates for actual steroid dehydrogenase activ ity. Copyright (C) 1999 John Wiley & Sons, Ltd.