Ceramide synthases (CerS) catalyze ceramide formation via N-acylation of a sphingoid base with a fatty acyl-CoA and are attractive drug targets for treating numerous metabolic diseases and cancers. Here, we present the cryo-EM structure of a yeast CerS complex, consisting of a catalytic Lac1 subunit and a regulatory Lip1 subunit, in complex with C26-CoA substrate. The CerS holoenzyme exists as a dimer of Lac1-Lip1 heterodimers. Lac1 contains a hydrophilic reaction chamber and a hydrophobic tunnel for binding the CoA moiety and C26-acyl chain of C26-CoA, respectively. Lip1 interacts with both the transmembrane region and the last luminal loop of Lac1 to maintain the proper acyl chain binding tunnel. A lateral opening on Lac1 serves as a potential entrance for the sphingoid base substrate. Our findings provide a template for understanding the working mechanism of eukaryotic ceramide synthases and may facilitate the development of therapeutic CerS modulators.

中文翻译：

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真核神经酰胺合酶复合物的结构和机制

神经酰胺合酶 (CerS) 通过鞘氨醇碱基与脂肪酰基辅酶 A 的 N-酰化来催化神经酰胺的形成，是治疗多种代谢疾病和癌症的有吸引力的药物靶点。在这里，我们展示了酵母 CerS 复合物的冷冻电镜结构，该复合物由催化 Lac1 亚基和调节性 Lip1 亚基组成，与 C26-CoA 底物复合。CerS 全酶以 Lac1-Lip1 异二聚体的二聚体形式存在。Lac1 包含一个亲水反应室和一个疏水通道，分别用于结合 CoA 部分和 C26-CoA 的 C26-酰基链。Lip1 与 Lac1 的跨膜区和最后一个腔环相互作用，以维持适当的酰基链结合通道。Lac1 上的横向开口用作鞘氨醇基底基板的潜在入口。我们的研究结果为理解真核神经酰胺合酶的工作机制提供了一个模板，并可能促进治疗性 CerS 调节剂的开发。