Cytochrome b5: Novel roles in steroidogenesis

► Mutations in cyt-b5 cause true isolated 17,20-lyase deficiency. ► Cyt-b5 induces a conformational change in CYP17A1. ► Cyt-b5 augments the activity of 3βHSD by increasing the enzymes affinity for NAD+. ► Cyt-b5 is forms homomeric complexes in living cells.