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Exploring and Exploiting Acceptor Preferences of the Human Polysialyltransferases as a Basis for an Inhibitor Screen
Author(s) -
Ehrit Jörg,
Keys Timothy G.,
Sutherland Mark,
Wolf Saskia,
Meier Chris,
Falconer Robert A.,
GerardySchahn Rita
Publication year - 2017
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201700157
Subject(s) - polysialic acid , sialic acid , enzyme , biochemistry , chemistry , biology , cell , cell adhesion , neural cell adhesion molecule
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.