5beta-cholestan-7alpha-ol-3-one is reduced to 5beta-cholestan-3alpha, 7alpha-diol

5Beta-cholesten-7alpha-ol-3-one and NADPH + H+ form 5beta-cholestan-3alpha,7alpha-diol and NAPDP+. The reaction is catalyzed by 3alpha-hydroxysteroid dehydrogenase (AKR1C4), a cytosolic enzyme belonging to the aldo-keto reductase family (Dufort et al. 2001). Biochemical studies with rat proteins raise the possibility that other related enzymes may also carry out this reaction in vivo (Russell 2003).

5β-胆固醇-7α-醇-3-酮与NADPH + H+反应生成5β-胆固醇-3α,7α-二醇和NAPDP+。该反应由3α-羟甾体脱氢酶（AKR1C4）催化，该酶为细胞质中的醛酮还原酶家族成员（Dufort等，2001年）。利用大鼠蛋白质进行的生化研究提出了可能性，即其他相关酶也可能在体内执行此反应（Russell，2003年）。