Nucleic acid, expressionvector and compositions for the identification and synthesis of recombinant sialyltransferases

The present invention relates to a recombinant polypeptide comprising siilyltransferase enzyme activity, wherein the polypeptide enzyme comprises a single catalytic domain, characterized in that the catalytic domain is selected from Cys-Arg-Arg-Cys-Ala-Val-Val-Gly-Asn-Ser-Gly- Leu-Lys-Glu-Ser-Tyr-Tyr-Gly-Pro-Gln-Ile-Asp-Ser-His-Asp-Phe-Val-Leu-Arg-Met-Asn-Lys-Ala- -Gly-Phe-Glu-Ala-Asp-Val-Gly-Ser-Lys-Thr-Thr-His-His-Phe-Val-Tyr-Pro-Glu; Cys-Ile-Val-Gly-Asn-Gly-Gly-Val-Leu-Ala-Asn-Lys-Ser-Leu-Gly-Ser-Arg-Ile-Asp-Asp-Tyr -Lys-Asp-Val-Gly-Ser-Lys-Thr-Thr-Leu-Arg-Leu-Asn-Ser-Ala-Pro- Arg-Ile-Thr-Tyr-Pro-Glu; or Gly-Gly-Asn-Ser-Gly-Val-Leu-Asn-Ser-Gly-Cys-Gly-Gln-Glu-Ile-Asp-Thr-His- - Ser-Phe-Val-Ile-Arg-Cys-Asn-Leu-Ala Pro-Val-Gln-Glu-Tyr-Ala-Arg-Asp-Val-Gly-Leu-Lys- Thr-Asp-Leu-Val - Thr-Met-Asn-Pro-Ser; a conserved homology region having amino acid sequence and variants thereof, wherein at least 58% of the amino acids are preserved in the conserved homology region of the sialyltransferase enzyme and wherein the catalytic domain has at least one amino acid having a site that is empty or substituted by another amino acid or which is catalytic domain- enzyme? -galactoside? -2,6 - siilyltransferase activity is absent. ŕ where at least 58% of the amino acids are preserved in the conserved homology region of the sialyltransferase enzyme and wherein the catalytic domain is at least one amino acid having a site that is empty or substituted by another amino acid or which is catalytic domain-ligated and wherein the enzyme? -galactoside? -2,6 - its sialyltransferase activity is absent. ŕ where at least 58% of the amino acids are preserved in the conserved homology region of the sialyltransferase enzyme and wherein the catalytic domain is at least one amino acid having a site that is empty or substituted by another amino acid or which is catalytic domain-ligated and wherein the enzyme? -galactoside? -2,6 - its sialyltransferase activity is absent. ŕ