CMP-DEPENDENT SIALIDASE ACTIVITY

摘要

The present disclosure is directed to the properties of certain glycosyltransferase variants having N-terminal truncation deletions or internal deletions. Any of the mutants disclosed in here exhibit α-2,6-sialyltransferase enzymatic activity in the presence of CMP-activated sialic acid as co-substrate, and in the presence of a suitable acceptor site. A fundamental finding documented in the present disclosure is that suchs enzyme are not only capable of catalyzing transfer of a sialidyl moiety but they are also capable of catalyzing hydrolytic cleavage of terminally bound sialic acid from a glycan. Particularly it was found that in the presence of cytidine 5'-monophosphate (CMP) glycosyltransferase activity is inhibited, and sialidase activity is stimulated. Sialidase activity was found to be dependent on the presence of a particular stretch of amino acids (position 90 to 108) in the polypeptide sequence of the reference (wildtype) hST6Gal-I polypeptide. Deletion of this sequence portion in an N-terminal truncation variant was found to abolish sialidase activity, notably both in the presence and in the absence of CMP. Thus, disclosed are compositions, uses and methods employing the CMP-mediated feed-back regulation documented herein.