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Autocatalytic polysialylation of polysialyltransferase‐1.
Author(s) -
Mühlenhoff M.,
Eckhardt M.,
Bethe A.,
Frosch M.,
GerardySchahn R.
Publication year - 1996
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1996.tb01086.x
Subject(s) - biology , autocatalysis , biological evolution , computational biology , evolutionary biology , genetics , biochemistry , catalysis
Polysialic acid (PSA) is a specific and highly regulated post‐translational modification of the neural cell adhesion molecule NCAM. Synthesis of PSA depends on the activity of a single enzyme, the polysialyltransferase‐1 (PST‐1), recently cloned from three mammalian species. The present study was carried out to investigate the catalytic mechanism of PST‐1. Using a newly developed in vitro assay system, we demonstrate autopolysialylation for PST‐1. The synthesis of PSA chains, which involved N‐glycosylation sites, occurred immediately after contact with the activated sugar donor CMP‐Neu5Ac. In contrast to the polysialylation of NCAM, where terminal sialylation in either the alpha2,3 or alpha2,6 position is required, the autopolysialylation could be started in the asialo‐PST‐1 isolated from CHO cells of the Lec2 complementation group. Pre‐formed PSA chains were not transferred to NCAM. Nevertheless, the autocatalytic step is likely to be a prerequisite for enzymatic activity, since agalacto‐PST‐1 isolated from Lec8 cells was functionally inactive. Our data describe a novel route of autocatalytic maturation of a glycosyltransferase and thereby provide a new basis for studies aimed at elucidating and influencing the catalytic functions of PST‐1.