Ehrit Jörg, Keys Timothy G, Sutherland Mark, Wolf Saskia, Meier Chris, Falconer Robert A, Gerardy-Schahn Rita
Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany.
Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, West Yorkshire, BD7 1DP, UK.
Chembiochem. 2017 Jul 4;18(13):1332-1337. doi: 10.1002/cbic.201700157. Epub 2017 May 24.
α2,8-Linked polysialic acid (polySia) is an oncofoetal antigen with high abundance during embryonic development. It reappears in malignant tumours of neuroendocrine origin. Two polysialyltransferases (polySTs) ST8SiaII and IV are responsible for polySia biosynthesis. During development, both enzymes are essential to control polySia expression. However, in tumours ST8SiaII is the prevalent enzyme. Consequently, ST8SiaII is an attractive target for novel cancer therapeutics. A major challenge is the high structural and functional conservation of ST8SiaII and -IV. An assay system that enables differential testing of ST8SiaII and -IV would be of high value to search for specific inhibitors. Here we exploited the different modes of acceptor recognition and elongation for this purpose. With DMB-DP3 and DMB-DP12 (fluorescently labelled sialic acid oligomers with a degree of polymerisation of 3 and 12, respectively) we identified stark differences between the two enzymes. The new acceptors enabled the simple comparative testing of the polyST initial transfer rate for a series of CMP-activated and N-substituted sialic acid derivatives. Of these derivatives, the non-transferable CMP-Neu5Cyclo was found to be a new, competitive ST8SiaII inhibitor.
α2,8-连接的聚唾液酸（polySia）是一种在胚胎发育过程中高度丰富的癌胚抗原。它在神经内分泌起源的恶性肿瘤中重新出现。两种聚唾液酸转移酶（polySTs）ST8SiaII和IV负责polySia的生物合成。在发育过程中，这两种酶对于控制polySia的表达都是必不可少的。然而，在肿瘤中ST8SiaII是主要的酶。因此，ST8SiaII是新型癌症治疗药物的一个有吸引力的靶点。一个主要挑战是ST8SiaII和-IV在结构和功能上的高度保守性。一个能够对ST8SiaII和-IV进行差异测试的检测系统对于寻找特异性抑制剂具有很高的价值。在此，我们为此目的利用了受体识别和延伸的不同模式。使用DMB-DP3和DMB-DP12（分别为聚合度为3和12的荧光标记唾液酸寡聚物），我们确定了这两种酶之间的明显差异。这些新的受体使得能够对一系列CMP活化的和N-取代的唾液酸衍生物的聚唾液酸转移酶初始转移速率进行简单的比较测试。在这些衍生物中，不可转移的CMP-Neu5Cyclo被发现是一种新的竞争性ST8SiaII抑制剂。
