Sialyltransferase and dna encoding the same

Abstract

A sialyltransferase having the following physico-chemical properties: (1) Activity; transfers sialic acid from a sialic acid donor selectively to a 3-hydroxyl group of a galactose residue contained in lactosylceramide as a sialic acid acceptor to produce ganglioside G M3 ; (2) Optimal reaction pH: 6.0 to 7.0; and (3) Inhibition and activation: the activity increases at least 1.5 times with 10 mM of Mn 2+ as compared with the case in the absence thereof.

1 . An isolated sialyltransferase having the following physico-chemical properties:
 (1) Activity:
 transfers sialic acid from a sialic acid donor selectively to a 3-hydroxyl group of a galactose residue contained in lactosylceramide as a sialic acid acceptor to produce ganglioside G M3 ; 
   (2) Optimal reaction pH:
 6.0 to 7.0; and 
   (3) Activation:
 the activity increases at least 1.5 times with 10 mM of Mn 2+  as compared with the case in the absence thereof. 
   
     
     
         2 . The isolated sialyltransferase of  claim 1  having a C-terminal amino acid sequence shown by SEQ ID NO: 5. 
     
     
         3 . The isolated sialyltransferase of  claim 1  comprising the amino acid sequence shown by SEQ ID NO: 6. 
     
     
         4 . The isolated sialyltransferase of  claim 1  comprising the amino acid sequence shown by SEQ ID NO: 12. 
     
     
         5 . The sialyltransferase according to  claim 4 , wherein said sialyltransferase is derived from human. 
     
     
         6 . The sialyltransferase according to  claim 1 , wherein said sialic acid donor is cytidine 5′-monophosphate-sialic acid (CMP-sialic acid). 
     
     
         7 . The sialyltransferase according to  claim 1 , wherein said sialyltransferase is derived from human. 
     
     
         8 . The isolated sialyltransferase of  claim 1  comprising a polypeptide having an amino acid sequence selected from the group consisting of:
 (a) the amino acid sequence shown by SEQ ID NO: 2, and   (b) the amino acid sequence shown by SEQ ID NO: 2, which has therein substitution, deletion, insertion or rearrangement of one or a few amino acid residues.   
     
     
         9 . The isolated sialyltransferase of  claim 1  comprising a polypeptide, wherein said polypeptide has an amino acid sequence with not less than 65% homology with an amino acid sequence shown by SEQ ID NO: 8. 
     
     
         10 . The isolated sialyltransferase of  claim 1  having no transmembrane domain. 
     
     
         11 . The sialyltransferase according to  claim 10 , wherein said sialyltransferase has an amino acid sequence comprising SEQ ID NO: 8 with a transmembrane domain deletion. 
     
     
         12 . The isolated sialyltransferase of  claim 8  having the amino acid sequence of amino acid numbers 38 to 359 in the amino acid sequence shown by SEQ ID NO: 2. 
     
     
         13 - 21 . (canceled) 
     
     
         22 . The isolated sialyltransferase of  claim 1  comprising the amino acid sequence of amino acid numbers 41 to 362 in the amino acid sequence shown by SEQ ID NO: 8. 
     
     
         23 . The sialyltransferase according to  claim 22 , which comprises the amino acid sequence of amino acid numbers 1 to 362 in amino acid sequence shown by SEQ ID NO: 8. 
     
     
         24 . (canceled) 
     
     
         25 . The isolated sialyltransferase of  claim 1  comprising an amino acid sequence shown by SEQ ID NO: 11. 
     
     
         26 . An isolated polypeptide comprising an amino acid sequence of amino acid numbers 41 to 362 in amino acid sequence shown by SEQ ID NO: 8. 
     
     
         27 . An isolated polypeptide comprising an amino acid sequence of amino acid numbers 1 to 362 in amino acid sequence shown by SEQ ID NO: 8. 
     
     
         28 - 43 . (canceled)