Patent ID: 6838446

Claim:
An expression vector expressing a glycosylphosphatidylinositol (GPI)-enzyme hybrid anchored to a surface of a mammalian cell comprising: i) a polynucleotide sequence encoding a signal peptide; ii) a polynucleotide sequence encoding an enzyme which activates a prodrug; iii) a polynucleotidc sequence encoding a post-translational GPI addition motif; and wherein sequences i), ii) and iii) are functionally positioned in this order relative to each other in the 5′ to 3′ direction of the sense strand of the vector; the enzyme does not have a GPI addition motif where the enzyme occurs naturally; and whereby on expression of the vector in the mammalian cell, the enzyme is anchored to the surface of the cell via a GPI moiety post-translationally added to the enzyme by the mammalian cell whereby the GPI-enzyme hybrid is formed; and wherein the enzyme is carboxypeptidase G2 comprising unaltered glycosylation sites.