N-Terminal 112 amino acid residues are not required for the sialyltransferase activity of Photobacterium damsela alpha2,6-sialyltransferase.

Photobacterium damsela alpha2,6-sialyltransferase was cloned as N- and C- His-tagged fusion proteins with different lengths (16-497 aa or 113-497 aa). Expression and activity assays indicated that the N-terminal 112 amino acid residues of the protein were not required for its alpha2,6-sialyltransferase activity. Among four truncated forms tested, N-His-tagged Delta15Pd2,6ST(N) containing 16-497 amino acid residues had the highest expression level. Similar to the Delta15Pd2,6ST(N), the shorter Delta112Pd2,6ST(N) was active in a wide pH range of 7.5-10.0. A divalent metal ion was not required for the sialyltransferase activity, and the addition of EDTA and dithiothreitol did not affect the activity significantly.