Figure 5From: Mitochondrial 3 beta-hydroxysteroid dehydrogenase (HSD) is essential for the synthesis of progesterone by corpora lutea: An hypothesisThe proposed regulation of progesterone synthesis by pregnenolone and by extramitochondrial NAD+/NADH. In the overall conversion of cholesterol to progesterone, pregnenolone acts as an end product inhibitor in the P450scc reaction, [······ (-)]; and, in the mitochondrial HSD reaction, extramitochondrial NAD+ operates as an allosteric activator [------(+)] and extramitochondrial NADH operates as an allosteric inhibitor [······ (-)].Back to article page