Adenosine 5′-phosphosulfate kinase (APSK) catalyzes the rate-limiting biosynthetic step of the universal sulfuryl donor 3′-phosphoadenosine-5′-phosphosulfate (PAPS). In higher eukaryotes, the APSK and ATP sulfurylase (ATPS) domains are fused in a single chain. Humans have two bifunctional PAPS synthetase isoforms: PAPSS1 with the APSK1 domain and PAPSS2 containing the APSK2 domain. APSK2 displays a distinct higher activity for PAPSS2-mediated PAPS biosynthesis during tumorigenesis. How APSK2 achieves excess PAPS production has remained unclear. APSK1 and APSK2 lack the conventional redox-regulatory element present in plant PAPSS homologs. Here we elucidate the dynamic substrate recognition mechanism of APSK2. We discover that APSK1 contains a species-specific Cys-Cys redox-regulatory element that APSK2 lacks. The absence of this element in APSK2 enhances its enzymatic activity for excess PAPS production and promotes cancer development. Our results help to understand the roles of human PAPSSs during cell development and may facilitate PAPSS2-specific drug discovery.

腺苷 5'-磷酸硫酸激酶 (APSK) 催化通用硫酰基供体 3'-磷酸腺苷-5'-磷酸硫酸 (PAPS) 的限速生物合成步骤。在高等真核生物中，APSK 和 ATP 硫酸化酶 (ATPS) 结构域融合在单链中。人类有两种双功能 PAPS 合成酶亚型：具有 APSK1 结构域的 PAPSS1 和包含 APSK2 结构域的 PAPSS2。 APSK2 在肿瘤发生过程中对 PAPSS2 介导的 PAPS 生物合成表现出明显较高的活性。 APSK2 如何实现 PAPS 的过量生产仍不清楚。 APSK1 和 APSK2 缺乏植物 PAPSS 同系物中存在的常规氧化还原调节元件。在这里，我们阐明了 APSK2 的动态底物识别机制。我们发现 APSK1 含有 APSK2 所缺乏的物种特异性 Cys-Cys 氧化还原调节元件。 APSK2 中缺乏该元素会增强其酶活性，导致过量 PAPS 产生并促进癌症发展。我们的结果有助于了解人类 PAPSS 在细胞发育过程中的作用，并可能促进 PAPSS2 特异性药物的发现。