The conversion of 7-dehydrocholesterol to cholesterol, the final step of cholesterol synthesis in the Kandutsch-Russell pathway, is catalyzed by the enzyme 7-dehydrocholesterol reductase (DHCR7). Homozygous or compound heterozygous mutations in DHCR7 lead to the developmental disease Smith-Lemli-Opitz syndrome, which can also result in fetal mortality, highlighting the importance of this enzyme in human development and survival. Besides serving as a substrate for DHCR7, 7-dehydrocholesterol is also a precursor of vitamin D via the action of ultraviolet light on the skin. Thus, DHCR7 exerts complex biological effects, involved in both cholesterol and vitamin D production. Indeed, we argue that DHCR7 can act as a switch between cholesterol and vitamin D synthesis. This review summarizes current knowledge about the critical enzyme DHCR7, highlighting recent findings regarding its structure, transcriptional and post-transcriptional regulation, and its links to vitamin D synthesis. Greater understanding about DHCR7 function, regulation and its place within cellular metabolism will provide important insights into its biological roles.

7-脱氢胆固醇向胆固醇的转化是坎德施-罗素途径中胆固醇合成的最后一步，是由7-脱氢胆固醇还原酶（DHCR7）催化的。DHCR7中的纯合或复合杂合突变导致发展性疾病史密斯-莱姆利-奥皮兹综合症，也可能导致胎儿死亡，突出了这种酶在人类发育和生存中的重要性。除了用作DHCR7的底物外，7-脱氢胆固醇还通过紫外线在皮肤上的作用，也是维生素D的前体。因此，DHCR7发挥复杂的生物学作用，参与胆固醇和维生素D的产生。确实，我们认为DHCR7可以充当胆固醇和维生素D合成之间的转换。这篇综述总结了关于关键酶DHCR7的当前知识，重点介绍了有关其结构，转录和转录后调控及其与维生素D合成的联系的最新发现。对DHCR7功能有更深入的了解，