mithramycin dehydrogenase (NADPH) activity
mithramycin dehydrogenase (nadph) activity
Catalysis of the reaction: mithramycin DK + NADPH + H+ = iso-mithramycin + NADP+. Note that  iso-mithramycin (iso-MTM) is a C2-epimer of mithramycin.  This intermediate appears to be biologically important because it is non-toxic, then exported out of the cell and finally spontaneously epimerized into the toxic mithramycin. This could represent a self-resistance mechanism against MTM toxicity.