Enzymic reactions of the adrenal gland involved in the hydroxylation of carbons 17 and 21 of the pregnene nucleus.

Two enzyme systems have been demonstrated in beef adrenal homogenates. These systems will introduce the 17 alpha-hydroxyl group into the progesterone molecule and oxidize the 21-methyl group of progesterone to a primary alcohol. The characteristics of these systems have been studied and they have been adapted to the synthesis of c14-labelled adrenal steroids from labeled progesterone. The 21-hydroxylase system is the more stable of the two. It will retain activity upon lyophilization, is soluble in dilute salt solutions and has been partially purified by ethanol fractionation procedures. This system functions effectively in Krebs bicarbonate buffer if a hydrogen acceptor such as DPN or TPN is added to the incubation medium. ATP plus DPN has been noted to enhance the reactivity of this system over DPN alone. The 17-hydroxylating system is comparatively labile. It, too, is soluble in dilute salt solutions but will not function unless both ATP and DPH are present in the incubation medium. Evidence has been presented for the possible existence of a steroid-phosphate intermediate compound in the pathway of this reaction. A scheme has been proposed based on the findings of this investigation which can be adapted to explain the terminal biosynthetic steps for the non-benzenoid steroid hormones.